You are right to be concerned about Polybutylene pipes. I have seen some severe problems caused by the failure of the connections of these plumbing systems, and expect that there will be many more. The class action suit has expired so, if you end up with a house with polybutylene pipes, you're on your own.
Have the home inspected by an inspector who is not afraid to call it like it is. Plolybutylene piping systems need to be replaced with copper piping, or the material will oxidize and deteriorate until connections break and pipes crack in the walls. Polybutylene piping was used from 1978 until 1995, but most homes in the Albuquerque area didn't get built with it until the mid-80s. The homes on the west side have it the most because that's where Albuquerque and Rio Rancho were growing the most during the time polybutylene was being used. All builders used polybutylene in the Albuquerque and Rio Rancho areas during the 1980s and into the 1990s. I have found polybutylene piping in all price ranges of homes, and even in additions built onto existing homes.
A qualified home inspector will discover the presence of polybutylene pipes, but they may have a disclaimer in their report which does not require them to report it, or they may just report it but play it down as not being a real problem. Make sure that your inspector is working objectively, and is not just helping to get the deal closed. My website has more information about choosing a home inspector.
Identifying polybutylene piping is not as easy as they make it sound. You can look for the grey pipes, but when it is used in the cabinet as a riser to a sink without the metal clamp type connectors, it is ok. Many installations don't have readily visible polybutylene pipes because its under the floor slab, and they used copper stub outs at the sinks. If the copper pipes under the sink are easily moved, (polybutylene pipes are somewhatt flexible), further invesitigation is needed. The inspector will check around the water heater and other areas, where piping may be exposed. Many, but not all, polybutylene piping installations will have a manifold inside an access panel in the wall of a closet.
Re-plumbing with copper pipe can be very expensive, especially if the home is built on a slab with no crawl space or basement.
I hope thiis helps.