I used to live in this area of Italy, so here goes.....
The San Marino WSB is at Circuito Misano is it not? If thats correct then you could fly to Bologna and then hire a car and drive down the Autostrada and it goes right past it (you can see it from the Autostrada)
Alternatively, if you were on the bike you could go Mont Blanc tunnel, Milan, Bologna and then down the Autostrada to Misano.
When I lived there, one of the cheapo air carriers flew to Rimini - Ryan Air I think. You could go with them and then get a taxi from Rimini to the circuit.
The race is in June, so bank on it being hot!