I am going to visit my sister in Dallas and would like to rent a bike anybody know of some places?

Richardson Bike Mart seems to be highly regarded online (I haven't shopped there myself), and I note on their website that they rent bikes. The store in Dallas is up the road a ways from White Rock Lake if you want to ride there:
http://bikemart.com/page.cfm?pageID=152

I don't know if the RBM location near WRL has many if any rentals, but I do know that the Richardson location does. Decent bikes too from what I've seen.

Thanks will checking them out when I get there.

Dallas Bike Works (http://www.dallasbikeworks.com/) is in NE Dallas. I know they have rentals, also. Not sure if the selection is as big as RBM.