I would vote for the BP causing the headaches, also. I almost never get headaches when non-preg., but get them pretty regularly when preg. I take my BP a lot (too much probably!) and often see that when it's high, I get a headache soon after, but haven't really seen a time when I took it when I had a headache, then my BP went up. But I would guess sometimes headaches CAN raise BP, esp. migraine headaches (which I don't have but know a lot of people who do).
I would take your cuff on the trip, just because if you don't, then that's always the time you wish you did! That is how it works with my sons' nebulizer for asthma---if we don't bring it, it seems like we need it, if we do, we don't! Plus checking your BP daily can't hurt anything! Have a good trip!
Suzanne (37) and DH Tony (41) + William (9, severe PE, born at 32 weeks) and Freddy (6, fairly typical pregnancy) and Baby (due approx. 8/26/04!)