Went to Pomona the year before last for the LA Roadster's show and swapmeet in June. Bought quite a lot of stuff at the swapmeet; I was buying SBC stuff mostly but there was lots of flattie stuff on sale as you'd expect. As well as the main event, local rodshops, SoCal etc. hold open evenings during the show week which are really interesting to visit.
For accomodation, depends what you're looking for really, there's plenty of low cost motels etc. nearby, we had no problem finding a room during the show week, so you might want to sort somewhere you're comfortable with once you've arrived there. We found that downtown Pomona was a bit rundown, and struggled to find anything other than Mc Donalds type places to eat in the evening without taking a long drive.