If possible i would get the 16-35f/2.8 or the 17-40f/4 i know you lose out on the IS but you'll have sharper images, plus you'll be able to upgrade to FF when possible. Since your going to Spain i think its more important to carry just 1 lens, by keeping the lowest profile possible and insurance that covers left/damage over seas. If you can only take 1 lens but don't mind the EF-s 18-200f/3.5-5.6 IS is an ok choice some barrel distortion at wide angle. Just the idea of losing an L lens over seas without protect makes me ; ;. 70-200/f4 IS will suit you fine, the extra weight from 2.8 will be very heavy and your arms will be dead half way threw the day. Don't see a very good reason to need the 2.8 since you'll be outside when using it.(1.6 crop on 70-200 inside a bar/hotel ext isn't gonna do well when you need some wide angle). Again if i can only take 1 lens maybe 2 keep it hidden and keeping a low profile. I would take 18-200/f3.5-5.6 ef-s if just 1 lens. If 2 16-35/f2.8(for inside wide angle and extra stop of light might be needed) or 24-105/f4 IS and i would take a 70-200. But it depends where I'm going and where I'm at. Google should help give you an idea where you are going and help plan out what gear you need. Don't forget extra memory cards!