Does iPad2 have a GPS receiver?

Depends:

If its a Wifi only model, then no.

If its a Wifi + Cellular (3G) model then yes as the GPS chip is part of the Cellular hardware.

iPad 2 Specifications

http://www.apple.com/ipad/ipad-2/specs.html

Only the cellular models have a built-in GPS chip, the wifi-only iPads don't (they rely on getting their location from the router that they are connected to being Apple's database, though some external GPS units work with them).