Getting a guide to any Euro city is easy. Just post an add on Elance.com in the "writing and translation" category. You'll have a dozen bilingual American ex-pats bidding to be your guide. Expect to pay between 10 and 20 dollars an hour.
Also, in Barcelona you can go to Travel Bar, right off the Ramblas and every day they have a different type of guided tour available (mostly centered around drinking, but also some other tour stuff.)
There is also a tour bus that starts right in front of the Hard Rock Cafe at the top of the Ramblas.
Barcelona really doesn't require much of a guide however. My advice:
1. Take a cab to the ramblas. Walk down it until you get to the port. Between the port and the ramblas, you've seen 80 percent of the good tourist stuff in the city.
2. Take a cab to Sagrada Famillia. Don't bother paying to see the inside of it, which is simply a construction site.
3. Take another cab to the Gaudi park. (I forget the name but it's easy to look up.)
4. Take another cab back to the ramblas. Walk two thirds of the way down the ramblas, turn left, walk two blocks and you are in the gayborhood and will be surrounded by gay bars, gay club, saunas and good restaurants.