The ATC coverage area for PE is the Los Angeles ARTCC (soon to include the Oakland ARTCC, too). By definition, no ATC is available outside of those areas.
Ideally, pilots will conduct flights that are entirely within the coverage area, or perhaps conduct flights that originate and/or terminate within the coverage area. This will help contribute to the traffic density and radio traffic.
That said, the radio system does work anywhere on the planet, so if there's a specific desire to fly elsewhere, either with a group of pilots, or as a solo flight, the system certainly supports it and pilots are well within their rights to do it.
Note: this post was significantly edited 2/22/12 to reflect in response to recent pilot feedback.