Yes, it is easy to be based in Sitges instead of Barcelona. Sitges is almost like a suburb of Barcelona.
You can easily make day trips or a 2 day trip to Barcelona for the main sights. Spend the rest of your time on the Sitges beaches and in the countryside of Garraf and Penedes.
Travel between Sitges and Barcelona
Travel from Sitges to Barcelona is convenient, fast and cheap. Trains from Sitges to Passeig de Gracia in Barcelona take only 40 minutes, and a round trip costs less than 10 Euros.
If you buy the T10 card for Zone 1,2,3 then it can be used for your commute between Barcelona city centre (zone 1) and Sitges (Zone 3).
Places to see around Sitges
Apart from the many undiscovered beaches around Sitges, there are a number of small towns in Catalonia which are easy to visit from Sitges
Famous for its beaches, nightlife and food, this ancient Roman city of Tarragona is only 45 minutes south of Sitges. There are many Roman ruins and a good Archeological Museum.
Dominated by the ancient Castle de Fels, this seaside town just 20 minutes north of Sitges is a nice place for watersport. The Marina in Castelldefels hosted events in the 1992 Olympics.
South of Sitges, 20 minutes and across the Garraf Natural Park is Vilanova. Points of interest are the Can Papiol Romanticism Museum, Catalonia Railway Museum, and The Vilanova Heritage Museum, apart from the beaches and promenade.
This university town with its famed river Onyar and University, is 2 hours north of Sitges. It is a bit of a stretch for a day trip unless you are planning to spend the night in Girona and see the towns (Figures, Tossa de Mar) in the surrounding areas.
The monastery of Montserrat on the serrated mountains is just one hour inland from Sitges, a great day trip idea. See the Black Madonna, L’Escolania boys choir, ride the Aeri de Montserrat cable car and the Montserrat Funicular to the famed hiking trails.
I am a big fan of being based in Sitges instead of Barcelona.
Stay in Barcelona, not in Sitges
Unless you hate Barcelona or have been there for long trips many times and want a change, I see no reason to stay in Sitges.
Sitges is nice but has only 2 things : beaches and glamour
Barcelona is right next door, it has so much more to offer for everyone. And you can literally hop across in 30 minutes to Sitges as many times as you want.
Sitges is not cheap
Some people say Sitges accommodation is cheaper but that is incorrect. Nice places in Sitges can cost as much as in Barcelona.
And it is far easier to walk back to your apartment or hotel after a late night in Barcelona, than it is to go back all the way to Sitges.