Montlake Bikes has rentals.
They're in Kirkland (adjacent to Bellevue) and in Seattle (just across Lake Washington).
http://www.montlakebike.com/rentals.php

Gregg's Cycle has rentals too but their Bellevue store doesn't.
http://www.greggscycles.com/cartgeni...sp?category=28

Montlake Bikes in Kirkland is the only place on the Eastside I know of that rents bikes.
Sammamish Valley Cycle in Redmond might.

Bellevue Bike map here.
http://www.onelesscarbellevue.org/su...bikewalk.shtml
Considering the type of city Bellevue is, it's surprisingly bike friendly.

You can ride across the I-90 bridge to Mercer Island and on to Seattle. The 520 bridge is cars only.