McAllister might not be the top destination in San Antonio if it's the only stop on your list, but if you are going to be there for something else, you need to drop by for some fun.
The park is essentially a winding spaghetti bowl of trails, most of which are pretty tame by all standards, but make for a fun afternoon of riding fast through the twisting trails. Try to ride the whole thing without riding the same trail twice can be difficult because it's such a maze. Once you get out and head East (I think) you get into a different terrain that is basically singletrack through a Texas grass land. The growth was so thick that my fork was getting hit on both sides by brush. Couldn't see the trail at all in some places.
The terrain is pretty light and there are no climbs and maybe 3-4 technical ledges (that I encountered). Unfortunately I came around a corner and was greeted by a construction crane. Damn progress!
For an afternoon of quick trail riding, Mac can't be beat, if you want a challenge with your speed, check out some of the other San Antonio trails.
Location: San Antonio, TX
Directions:Take I-35 south to I-410 west. Follow 410 to 281 and head north. Get off at the Bitters exit and follow that to Jones-Maltsburger Road (mmmmmm, maltsburgers.....) Follow that North to the entrance of the park which is on your right. Don't go to the first entrance, wait until you pass the Police substation, and then you'll see another entrance about 4-500 feet past that on your right. Drive towards the back near the sports fields. You'll see the trail cross the main road.