I am *G from both UA and CO, and live in Houston, so I checked the Continental President's Club access policy on their website:
http://www.continental.com/web/en-US...ge/access.aspx
Credentials required to enter for *G:
OnePass Platinum or Gold Elite card or MileagePlus Premier Executive or 1K card
Photo ID
One of the following:
Departing international Star Alliance boarding pass
Domestic Star Alliance boarding pass connecting to a same-day international Star Alliance itinerary
SO, to tie in back to the OP ... if you're A3 *G flying on an economy ticket within the US (say LAX-IAH-ORD), you would not be allowed into the PC in IAH. This is why many *G's who travel domestic USA buy club memberships.