I am heading to San Antonio in a few weeks. We will be staying in the northwest (by highway 410 and 10 and the Crossroads Mall). We will have a car but I was wondering if it would be cheaper (save on gas and parking) and easier to take a bus to the Riverwalk? Also are the buses safe? We will mainly be using them between like 8am and 9pm.

Check out schedules at
www.viainfo.net/BusService/Schedules.aspx

bus route #92. 30min ride from Crossroads Mall park & ride to downtown (a couple of blocks from the Riverwalk).

I never thought I would recommend the bus for visitors but in your case it may make sense. Once downtown you can stroll or jump on one of the trolleys that make a circuit around town. Crossroads is a major transit center for the Via bus system. You will have to walk at least a few blocks to your hotel, through not particularly attractive parking lots. (Which hotel are you using?) If your visit is during our annual Fiesta and you want to get downtown on the day of a parade definitely take the bus.

I have no clue when the fiests is but we will be there March 17-20th. We are staying at the Howard Johnson. We also don't mind walking a bit if it saves the hassle of parking and driving.

Your dates will not be during Fiesta so no worry about parade traffic.
This HoJo is located on an access road close to where IH10 crosses Loop 410. Crossroads transit center is on the other side of the freeway, and to get to it you would need to cross the access roads on both sides and walk under the elevated freeway. It is a busy freeway with a mess of construction going on but not far.
If you are dead set against driving it should not be that bad. However, if you would like to see more than the Riverwalk (such as the historic missions south of downtown) a car would be much better. Parking downtown is not truly cheap, but neither is it comparable to rates you see in New York or other large cities. At the missions parking is free.

lindy - I drove by there yesterday. The construction is in full bloom so there is a mess between you and the transit enter. Maybe the hotel has a shuttle? It's really not far, but everything is ripped up and traffic can get nasty. Be careful if you do try to walk across to the bus center.