There's a few options. The toll road option would probably be the worst of them all. You can take 50 all the way from 19 or 275 or 75 or any north/south road basically and go all the way out to the east coast on it, or you can take I4 and get off at the SR 50 (Colonial Dr.) exit in Orlando (exit ~85) and take that to the coast, but the best way would probably be I4 to 407 (exit 82a, a couple bucks in tolls), get off at the colonial exit and take that to the coast. From 50 you can get on US1 and get the space center.