I am traveling by ALSA bus service in Spain this summer, and was hoping someone could tell me how much luggage is allowed per person, is a large suitcase (kind w/wheels) going to be a problem? Thanks:)

I've taken about a dozen trips on Alsa and have never had a problem stowing luggage down below. I've traveled fine with the following luggage:

One 26" pullman
One large garment bag
One "gymnasium-style" duffel bag (brought on board with me)

You may want to check luggage allowances on their website, but you shouldn't have any trouble with 2-3 pieces of luggage (per person).

I've traveled via the ALSA Supra bus service where you are actually given baggage checks. Sometimes they do enforce the two checked bags per person limit. As far as carry ons are concerned, there is very limited space in the overhead rack , like for a small flat package or jacket!