We did the RS's Spain and Morocco tour fall 2012. My husband and I wanted to see both as well - so we arrived two days in advance. We stayed at the Hotel Barcelona Centro. We did not need a car at all.
For Monsterrat (detailed in RS's Spain book) we purchased the 'Tot Montserrat' tickets online while still in the states and picked up the tickets at the underground ticket office in the Plaça de Catalunya.
The morning of our Monsterrat trip (with tickets in hand) we head out. The To get to Montserrat, we travel to by Metro, train and cable car. The first train to Montserrat is at 8:36am. Our instructions caution us to give ourselves extra time as the signage for the Metro to the train (R5) is lacking. Sure enough, our Tot Montserrat ticket wouldn’t work in the turnstile. We ask for directions and were told by the attendant we entered the Metro at the wrong station. The Tot Montserrat Metro only works at the Catalunya station. We had to go back up to street level and walk five minutes to the Catalunya station. We were disoriented and since the sun wasn’t up yet, we couldn’t get our bearings. Finally, we arrived at the right station at Placa d’ Catelunya and take the Metro to the Espanya stop.
Here’s where it really got tricky (fortunately, we still had plenty of time until the 8:36am train to Montserrat). We ask an attendant in a booth how to get to FGC R5 line. He instructed us to go up to street level, go right, and in front of a hotel is the entrance. ---OK???? The instructions didn’t sound quite kosher, but we follow them. Above ground, the only hotel we saw was more left than right, so we cross two streets and went back down the stairs and voilà, R5.
Thank goodness we found our train with time to spare. It was overcast, so the views weren't great but the everything else was wonderful.
Again, stateside, we booked tickets via Viator for Cadaques and Figueres. After eating breakfast at the hotel around 7am we walked a short distance (less than 5 minutes) to our pickup location for the tour of Figueres and Cadaques, Spain. We headed out of Barcelona at 8:44am on the tour bus for Figueres. We toured both the theater/museum and a jewelry museum then got back on the bus for the ride to Cadaques. Lunch was on our own. To see Dali's home was an additional $11€ (totally worth it as it is just as Dali left it after his wife Gala died) - others just walked around the fishing village. Then it was a 90 minute ride back to Barcelona.
I wanted to visit Monsterrat; my husband is a huge Dali fan. We compromised by seeing both. Happy choosing; better yet see both!
P.S. Some folks like Viator; others don't. Over the years, we used them several times for tours and have been very satisfied. They are a consolidator and not the actual tour provider, nevertheless, our experience has been good.