Yes.  Most GPS models are easy to move between vehicles. If this is your plan, you'll need to give some thought to the mounting system and power supply.  Temporary mounting systems such as a suction cup or friction mount work with pretty much any vehicle.  Models powered by batteries or from a cigarette lighter provide the most flexibility.

If you plan on taking your GPS unit out of the vehicle, then battery power is very important.  Batteries are expensive so make sure that they are rechargeable and have a reasonable charge life (at least 8 hours of continuous use).  If they are not rechargeable, make sure to budget for after market rechargeable batteries and a battery charger.

Global Positioning System. A space-based radio positioning system that provides GPS receiver users with accurate position, velocity, and time data. GPS provides this data free of direct user charge worldwide, continuously and under all weather conditions. The GPS constellation consists of 24 orbiting satellites, with four equally spaced around each of six different orbital planes. The systems is developed by the USA Department of Defense under US Air Force management, primarily for military purposes, but current policy calls for civil availability with degradation in system accuracy to protect U.S. national security interests.