Based on reviews here and my limited experience here, there's a strong DG community here - probably the busiest course I've ever played and that was during a drizzly weekday midafternoon with storms looming. When we arrived to course, we were welcomed by an older gentleman who proceeded to "indoctrinate" us to the course and gave us a hand drawn map. He also gave us some throwing tips after seeing my less-than-stellar drive on the first hole (in my defense, it was my first time throwing in 2 years).
The course flows through grassy park with interspersed trees. Several holes are blind. I imagine that I could play a slightly different course each time with two concrete tee boxes ("metal" & "wood") and two targets at each hole (I think each hole had two targets, may be mistaken) and multiple hole locations.
We did not have time to play the 9 X holes in the woods.

Sometimes not clear where target is, though there is a map at the "metal" tee and a system identifying which hole placement the basket is in using a pipe clamp on the sign post. And finding next tee not always clear. See Links/Files tab here for course maps. Road (OB) potentially in play on a few holes for errant tossers.
Can be crowded with DGers and others walking through. Given location and activity in/around park, I'll be mindful when I play.

Update - this has become one of our go to courses this season. We generally play the "metal" (short) tees to the yellow baskets which are in the longest position but easiest to see because the old Mach5 baskets blend in. I haven't found distance and par info for several of these holes. I've come to really like this course. Given it's park setting, it offers as much variety as is possible, takes advantage of elevation and obstacles. There are good challenges but also several birdie opportunities.

Course has a good variety of holes. Some open fairways, but most have some type of tree obsticle. Couple of holes have elevation gain/losses.

Holes are tightly packed, but not too close.

Baskets seem to rotate from A-B-C locations fairly regularly.

Holes are easy to find and follow.

There are an extra 9 holes (X-Holes) that go through a heavily wooded area. These holes are a nice "change of pace", but can be a little hard to follow.

Front 9 and back 9 start from same location. If one is too crowded, you have the choice to start on the other.

Course usually has players on it. Easy to join with a group if playing alone.

No real negatives about the course except that the "A" basket positions tend to be very short. Upside is that the "A" basket positions allow for the possibilities of hole in ones

Most negatives are with the upkeep and non golfers near the course

Have been times where the course can get littered with nasty types of urban trash. Things you don't want to touch or have your disc touch.

Quite often, people (non golfers) will sit in their cars for long periods of time on roads near holes. Can be a little spooky.

Druid Hill Park is a huge urban park that, for the most part, is nicely maintained. There are other activities, like hiking and biking, that can be tied with golf to make it a full day of outdoor activity

27 holes, and over 30 baskets. Always someone playing. Great place to practice your game.

Grass is always high everywhere, always strange people sitting in their car. Used condoms and trash are a common sight while walking. Aside from the derelicts hanging around the road of the park, and the numerous homocides the area is no stranger of... I'd say your safe until the street lights come on.

Lots of holes, lots of activity. Great park for being in the middle of Baltimore city. The park is decent for being so old.

The park is very pretty, with rolling open slopes dotted with majestic trees. The course is well laid out, with little overlap between holes, and relatively intuitive flow from hole/hole. Most holes play differently form each other, so there is no feel of sameness.

Tees get muddy in wet weather. Limited parking.

Most holes are relatively short, and the more open nature of the park means that tree obstacles are usually not a significant challenge. This makes the course a good beginer course.

Several years ago the course managers extended several of the holes near the central woods region, which put them into a lot of poison ivy. I was pleased this year to see the PI had been eradicated.

Concrete tee pads and multiple tees. Multiple basket positions.
Nice amount of obsticles for any level player. Chance of dics loss is there, but very slight unless you need to take a risky shot. holes 18-27 are more isolated, wooded, and interesting (but not on the map)

There were tees and baskets everywhere! I always second guessed if I was heading to the right baskets and had to find the next tee. Signs are worn out and many baskets are not labeled. It is one of those courses you have to play numerous times to enjoy it with out confusion.
One of the tees for 7 was painted on the road and very hard to find.
More dogs than people out on the course and a few holes smelled strong of urine. An overflowing trash can of beer greeted guests at hole 1.
Several holes require you to throw across roads, walking paths and towards parked cars.

Course often holds tournaments on the weekends so check the schedule before visiting. Print out the directions to Rockburn just incase the course is too crowded.
(Course is very similar to Ellison Park in Rochester, NY)

Multiple Tees and Pins
well Maintained
Decent signs and teepads
Nice use of elevation
Large mature trees occupy the plot that was formerly part of the Baltimore Zoo - so it is very pleasing to the eye.
Beginner friendly, but also has the flexibility to provide a nice challenge for pro level players.
Very little impact from other park users - fairly isolated in terms of user groups.

Not such a good neighborhood - but surprisingly isolated so that neighborhood impacts are minimized.Still, be sure and lock your car and stow your valuables.
No bathrooms or water.

I reall enjoy this course. It's an easy walk, and has some beautiful holes. Not terribly difficult, but definitely fun. The locals run an interesting format called TNT (Thursday Night Triples) during the summer months, that gives newer players the opportunity to be teamed up w/local pros in a fun competitive atmosphere. Definitely worth a visit if your passing through Baltimore.