Mud Creek is a good trail to have in your backyard, but don't plan on making any road trips to ride it. The singletrack is nice, narrow, and winding. Many of the turns are quite tight and if you aren't paying attention, more than one overhanging or nearby tree will remind you to do so.
The parking is very limited, but once you get rolling you will head up the wide path to a right turn with large rocks encasing the path. As you follow this path you will see a trail that branches off towards the power lines - this is your first loop to choose from. Follow the trail up the hill and you will see clearly where the singletrack dips into the woods near the first tower.
Halfway through this loop the trail splits, though it isn't too obvious until you are practically on top of the split. One route will take you to the end where you will need to make a hard left (instead of crossing the dry creek which is a dead-end) that will take you on a stretch of doubletrack bringing you back to the tower you dipped into the woods at. If you manage to notice the other route at the halfway point, it will guide you down a rock/concrete "staircase" that makes for a fun drop (this will also bring you out near the other loop).
If you choose not to branch off of the main path to the above loop, you will follow the main path to a trail that heads off to the right (right before a concrete pyramid drain thing). Take this trail to a 'T' next to a big rock and turn left - enjoy the tight, twisting singletrack that Mud Creek has to offer. When you come back out to the main path, turn left and follow it back over a very rocky area and either do the loop again, or head back to the first loop.
Note: Where you come out from this loop is about 20 ft from where you would come out if you go down the "staircase." Get used to the trails and you can make it a figure 8. The other option for Mud Creek is to simply stick with the main path/doubletrack and do an out and back to 1604.
Mud Creek is definitely a little singletrack gem in San Antonio; unfortunately, it's all too overlooked with McAllister Park a mere mile away.