Given the extended universe canon, Hoth to Dagobah is probably a base duration of a few hours at most. They're nearly adjacent, according to the Essential Atlas maps.

Far more important is the travel time to/from Dagobah by Luke. The X-Wing has a week of consumables according to Wookieepedia and a x1 Hyperdrive. Since Luke makes it from Hoth to Dagobah and back to Bespin with under a week of endurance, this puts a much longer trip at 3 days each way or so. Moreover, Luke has the fuel to meet up with the fleet following this, reducing it further.

We don't know exactly how much time it takes for them to make the trip, but we do see Leia change clothes between Hoth and Bespin, so most likely, it was over a day... but with a x10 hyperdrive, that means only at least a 2 hour base trip time. There are implications of a period of time working on the Falcon before Vader reveals himself - and then a period of being tortured. A period of torture implied in the novelization to be high single digit days before Lando works up the nerve to talk to them.

We can see several levels of costume change on Luke, as well. The day he arrives, it's nightfall, and he eats with Yoda. We see portions of the next day. We see a change in costume indicating time passing. We then see Luke in the Tree. We see even more distress on the garments. We see Luke talking with Yoda about Han and Leia suffering. We see a change in outfit to a flight suit, and departure.

We can take as implied that there is at least 2-3 days between costume distress levels in the training. That gives us a few weeks. It's more likely that it takes longer than that.

We have also the Falcon's travel time. It's not much, tho' - even though the Falcon has a maximum of two months consumables, it's travelling on a backup hyperdrive. Backup Hyperdrives are, according to several sources, limited to several hours range... so we can't even account for missing time that way.

In any case, to make things match even a couple days per costume adjustment, the hyperdrives need to be pretty fast.

Also, it is worth noting that anything past about 12 hours makes for pilots in cramped cockpits having various forms of distress - it's hard to sleep in a chair, and in flight relief units are generally only good for urine.

I'd put my estimate between 7 and 21 days of training with Yoda, and about another 2 days of travel time for Luke

sample Atlas Map