I believe that you might be able to find lots of information from previous threads regarding San Antonio. We have stayed at Traveler's World, which is just south of the downtown area. It is not a fancy park, but seemed nice enough. We only stayed 2 or 3 nights. There is a public bus that picks up directly in front of the park and goes by the river walk. When we got on, we told the driver our intentions and he was helpful in letting us know when to get off. We thought it was a great plan, as parking is so limited in downtown and usually a bit of a walk to get to the populated area of the riverwalk.