Heading to Madrid... Vodafone sim in my 640 LTE dual sim?

[FancyFreddy]

So I flashed my 640 LTE DS with the FR rom and it works great here in the US.

Will I run into any issues if I stick a Vodafone sim (prepaid) from Spain into it, in terms of coverage, while I am there?

Is there one carrier over another for a prepaid service during a single week that someone can recommend? (co-workers are all using prepaid vodafone sims in their unlocked iphones and droids, some are using Orange)