Normal temp in a MacBook Pro while using an external screen
Those temps seem fine to me. 

The late 2011 MBP models usually range from about 40ºC (104ºF) to 100ºC (212ºF) depending on whether the CPU is idle or under load. CPU temps (just like ambient temperatures) typically have a bearing on GPU temps too, especially within the extremely confined spaces of a MacBook. 

If you're interested, you can check out the Intel Mac Temperature Database for an indication of the various temperatures that Intel Macs run at. Unfortunately the database doesn't separate out GPU temps, but it's still a useful guide.

That said, I do understand your concern considering your Mac's history. I would just keep an eye on those temps when you're in Oregon to see how much the ambient temperature affects things. But a GPU temp in the mid 70s (ºC) or high 160s (ºF) is nothing to worry about.