Oh... and... SOLO HAD NO LIGHTSPEED BUT MADE IT TO BESPIN!! PLOTHOLE!!!!
This has been discussed ad nauseum, but I'll explain the "No it's fine" side:
Bespin is not too far away from Hoth. Not in the same planetary system, but nearby. We do not know how long it takes them to get to Bespin. In fact, all we know for sure is that while they're en route:
- Luke trains with Yoda
- Boba Fett follows them without being noticed
- Vader waits for his bounty hunters to report back
Vader waiting has no real time problems. The man can wait with the starfleet doing Imperial things for as long as he needs. He's not likely to find the Falcon during this gap, as the Falcon is flying in the big empty spaces between star systems and that's just not very easy to search. Besides, he's counting on the bounty hunters to turn something up whenever the Falcon reemerges at spaceport from wherever they disappeared to (remember, Vader doesn't actually know where they went).
The longer Luke trains with Yoda, the more plausible ROTJ becomes, as he can learn loads and loads from Yoda, but only really get the practice and meditation he needs to be a Jedi in between ESB & ROTJ (thus explaining why he's not so much a Jedi during the ESB duel). This is, for me, the biggest thing in favor of the Hoth->Bespin journey being long.
As for the Falcon and Slave 1 flying for so long... They don't have hyperdrive, only their engines. Spaceship engines are never really well explained in Star Wars (because it's a space opera, thank god), so we don't actually know much about how much they can accelerate a ship, for how long, fueling, etc. However, if we assume that they just put the engines on FULL-GO-FAST for the whole trip, then perhaps we can say that they spend the whole trip accelerating up to as near lightspeed as they can go. Relativistic effects become noticeable, and the occupants of both the Falcon and Slave 1 experience a far shorter journey than Luke does while training. In this way, we solve their food problems.
No, I don't know how Fett manages to not be detected. Perhaps he follows (somehow stealthily) for a short period, long enough to get their heading and extrapolate where they're going, then turns off the engines andlets them fly away a little longer so they won't notice him when hyperdrives back to civilization to bounty hunter things. Later, knowing approximately when they'd arrive at Bespin, he informs Vader and they all hyperdrive to Bespin just before the Falcon arrives.
And yes, I'm introducing relativistic effects in a movie series where spaceships move like WWII fighter planes.