We're heading to Provo in about 5 weeks and the only full-day sailboat trip I've been able to track down so far is Sail Provo.

Are there any others? Anything on a monohull?

Check out J&B tours.

Would also recommend J&B. We did a full day sail that included a tour of the caves in Middles Caicos, lunch and swimming on a beautiful deserted beach, iguana island, snorkeling, and looking for sand dollars. They pick you up and drop you off right at your hotel on the beach. It was an awesome day!

I've looked at the J&B website before and it appears to me that these trips are on motorboats, not sailboats.

Is this incorrect?

You are correct we went on a motor boat, I didn't see the request for sailboat...sorry! We did do a sunset sail on a catameran, can't remember the company, but booked through our hotel, Ocean Club West. They started with the motor then put up the sails and cut the engine. Not familiar with any full-day sails, sorry can't be more helpful!