We stayed in a bed and breakfast about a 15 minute walk from the main "loop" of the River Walk and were glad we did. It is very lovely and fun to walk around and people watch, but it does get crowded in the afternoon and evening. We were there for the very beginning of Fiesta (by accident) so I don't know if it is always that busy or not. We took bought a water taxi ticket-good for 24 hours- and traveled to the end (Pearl Brewery) twice. The ride is lovely. Our first taxi captain was great and acted more or less like a tour guide, the the second one was not; never said a word for the whole trip. By the time our second trip was over, our ticket time had run out so we just caught a city bus back to town. It was very easy and our inn keeper had given us a free day pass.
We most enjoyed the parts of the River Walk that went north of the look and south back to the King William district, where we were staying, and even walked south from there one morning. It is all very well maintained and clean; lots of ducks and other birds unfamiliar to visitors from the Northwest.
We had snacks and drinks on the main loop a couple times, very pricey but a good place to hang out.