Hi Lizzie,
Haven't been to a MotoGP at any of them, but I'd go for Spain as you can catch some rays (no chance in Brno) and vaguely understand what people say (no chance in Estoril). There's also a raft of options for getting there, some great biking en-route, it's cheap, and it's just a damn fine country all round.
Hope you have a classic, whichever you end up at.
Cheers,
Ali
ps: thanks for the welcome pack, Prontos read cover-to-cover....