I've spent several months in Salt Lake City over the last couple of years for work. Lots of good trails out there, but the climbs are a bit longer and more exposed. Worth every second.
For ease of rental and all: go to Park City. There are 2 bike stores on Park Ave, (the main road leading into town). Ive used Cole Sports before but the store across the street looks good too. You may want to pack your helmet, shoes and peddles. There is plenty of trail that can be hit from the from the store. After your ride hit the No Name Saloon for a burger and beverage
For info on trails in Utah I like to use http://www.utahmountianbiking.com