Yeah, we just hit Prague during our Spring Break road trip. I live in Germany, and we drove as far east as Budapest, but in CZ we only really visited Prague.
Russian speakers are common, especially amongst the older people. The younger people can usually speak some English, but even in Prague, some only spoke Czech.
I have rented a car in several European countries over the past 18 months, and it has always been much cheaper than when I rent in the US. I've had very good results when I use Priceline. It might direct you to another site, but they have consistently had the best prices and selection of cars. Several credit cards cover you for insurance, but be sure to understand the terms. Reason for that is that European car rental agencies often give you a hard sell for additional insurance. If you do rent a car, use a reputable firm like Hertz, Avis, or Budget. Many of the no name companies in Europe have been known to rip people off, saying that they found damages after the car was turned in. I've never had a problem, using the companies I just named.
While unecessary and not recommended in Prague, driving in the rest of CZ is not a problem. The main highways are well maintained, better than most of the US, but not as nice as Germany. However, once you get off the highway in the countryside, it can be a very different story, with single lane bridges, and roads that are crumbling. I enjoyed the experience though.