I definitely recommend doing the River Walk Cruise. Short but sweet cruise around the River Walk with cool views and interesting facts about the architecture, city and businesses you can see from the boat. Definitely worth the money!
What sinks this review for us is the Hop On/Hop Off tour. I can't recommend this tour in San Antonio. Save your money and use a city bus to get to all these places and only do the River Boat tour if you want. First of all, the customer service is non-existent. We ordered our tickets online and it took over 12 hours to get our tickets e-mailed to us. This means you have to stop at the main office at the Alamo to pick up your tickets. What's the point, then? When we called to find out where our tickets were and to make sure the order went through, the lady was super short and did not listen. She did not offer a name or help and kept cutting us off whenever we tried asking a question. We actually helped her do her job by asking if she would like the confirmation number to look up our order. Otherwise, she was perfectly content just letting us go; basically pushing us off the phone. Very rude. The whole experience made us wish we could take our money back.
On top of that, there were only a couple buses running the day we went. So we spent a lot of the time on this tour waiting. Either waiting on the actual bus at the Alamo for 30 minutes or waiting at the bus stop at the Pearl Complex for 40 minutes. It sucked up a lot of our time. Therefore, we were unable to even come close to completing a full tour. One of our drivers lacked some insight into the city and frequently talked about things that weren't necessarily highlights of the tour. This same driver would also blow by the stops without actually really stopping or checking his camera/mirrors to see if people were coming down from the upper level. He would keep driving when people were trying to get off. People also aren't kidding about the the low-hanging branches that would do some serious damage to your face if you didn't duck your head. They really need to work with the city on that. We did have one other driver that was very knowledgable and wish we had him the whole time. So it's really hit or miss with your driver.
Hope this helps someone else!