Fog is our trademark, our natural air conditioning. Plenty of places to go and see, dress warmly, our weather changes a lot. The nicer places are near the airport or downtown, I would read all the reviews on this site and see what others say. Some nice motels are on SF streets that are impossible to park in and get around. San Francisco is beautiful, but you get what you pay for.
I have never had to rent a car and gotten around just fine.
It is very hot and dry, but Lake Tahoe, Donner Lake, and other beautiful areas can be reached by travel buses or tourist agencies and the weather is much better in my opinion. But if you want to avoid getting a car, ask the conductor about the Nugget and they fact that you don't have a car before you get to Reno. The two story motels are usually not too safe in my opinion ( Reno 911 is the local phrase) but there are some brand names that are fine. It is not California, Earthquakes are not a factor. As a former County Fire Chief, it is safe and Sparks has an excellent Fire/EMS system. They will give you a low level floor if you ask. Most low rise motels are being torn down or on skid row, the big hotels rule, however, without letting out my secret, I recommend you stay the Nugget.