There are a lot of balloon companies in the area. You'll find brochures on every rack. You could probably also find them with an internet search or by looking in the yellow pages.
It's almost a tradition for us that on the morning of our departure from Orlando we see balloons flying as we drive toward Hwy 27. It has happened countless times. We've also stayed in a few timeshares where they would fly over or by us while we were enjoying our morning beverages on the balcony.
I've never flown in Orlando, but have ridden in balloons several other places. It's a wonderful experience. I would guess that prices typically start around $150 per person.
Didnt do it in Florida but did it in Maine. The price was $175 per person, which included a ride of about 45-60 minute ride, and champagne toast after flight. I was given 2 free tickets and ended up taking my 15 DS along.