I've been to Brno twice, once for MotoGP in 2003 and WSB 2010 and really enjoyed both. MotoGP was packed, WSB wasn't at all, both times were scorching hot.
2003 we lucked out with accommodation and got somewhere within walking distance of the track at local rates, and made full use of the cheap beer at the track. Good food trackside too. We watched from area 'C', the big steeply banked area where a lot of people head for. Take/borrow a spade from someone to dig yourself a ledge to sit in to stop yourself sliding down the bank.
WSB is was far to hot to walk anywhere far so watched from the bottom of horsepower hill, area 'E'. Good view with few people there but might not be so good when packed.
Have a great time.