|I-35 Bridge by Camden and Newell|
During the month of August they give a series of special bat talks about...yes...BATS.
From these talks I learned that this is a bachelor colony (all boys, hehe) and that San Antonio has a couple maternal (girl bat) colonies as well, the Bracken and the Frio Caves. Male and female bats roost in different locations. These Mexican free-tail bats are migratory. They are usually present in San Antonio from April to October and move to Mexico in the winter. As you can see from the video below, the bats fly out from underneath the I-35 overpass for a short few minutes (about 20) and people gather in advance to get the best views. However, that's not difficult as there are thousands of the little buggers that flock out from the bridge cubbies. This I-35 overpass is by Camden and Newell Streets and is part of the new extension of the River Walk, next to a new art installation of illuminated fish.
Use this map and directions link to get you there from Hidden Valley RV Park.
There may be an advantage to bringing nose plugs. If you've never had the distinct privilege of visiting a bat cave, their guano (poo poo) is pretty strong.