The park is WOW (way out west). The big, big climbs are to the east but there is some climbing on the west side of the valley too (into the Oquirrhs). To stay flattish, you'll need to head east from the park, which will take you into suburbia and traffic. You could stay on the west side of the valley and go north; you'd hit rollers but nothing substantial.

Whatever you do, stay OFF of the Jordan River Bike Path (which is north of where you will be). Goathead city!

Here's a site with a bunch of rides, but most of them are east of I-15 (you will be west of I-15): http://www.saltlakecycling.com/showallrides.php

Check this route (the bike park where you will be is off of Old Bingham Highway, which shows up in the middle of the map):
http://www.saltlakecycling.com/showride.php?rideID=1029

Honestly, I don't ride out that way much...I generally stay north and east. I'll be around that weekend and if you find yourself with a lot of time I could chauffeur you on a ride in the northern part of the valley.