Ok, I hope you enjoy your trip but what specifically is (are) your question(s)?

The "river" is about 2.5 miles in total length with some 5 miles of walkway lining both sides of the river with shops, restaurant, hotels and places on interest along the entire length. So theres no particular hotel location that is necessarily better than the other nor "near it all". They are just "different" locations.

What type of hotel experience are you seeking? What hotel amenities are important to you? Have you visited the websites for each hotel? What do you like about each hotel and what do you dislike?

I want to be close to all restaurants, entertainment, "action."
i have stayed at the Mokara Hotel before and loved the location. It is the most expensive of the three (the only downside).
I don't know if the Hotel Valencia or Contessa are in a "quieter" part of the Riverwalk. I dont want to be walking 10-15 minutes to get to the restaurants/entertainment.

Mokara is the most centrally located along the river walk. Hotel Valencia is on Houston Street on the northern spur of the river - not really near anything. Contessa is located on the "southern loop.

Go to Google Maps and you can zoom in on the River walk to find the locations of each hotel and their proximity to points of interest.

http://www.sanantonioinsider.com/hotels/san-antonio-hotel-map.htm

Thanks for the help, Rich and RoamsAround!