Thanks for the suggestions - I should be in good shape. Although I have not yet opened the A/C access basement door, I see how I should be able to. Since that particular compartment does not have a bottom it looks like I can reach the locks with a screwdriver to release them.
During the very same trip this weekend, I had another basement door lock mechanism goof up. I had my daughter crawl through and unlock it (whew!). I was able to fix it easily, but now I am a little gun-shy - what the heck is up with the basement door locks??? I guess it was just their time...