Talk about whatever, respecting the rules established by Lemmygrad. Failing to comply with the rules will grant you a few warnings, insisting on breaking them will grant you a beautiful shiny banwall.
A community for comrades to chat and talk about whatever doesn't fit other communities
Everyone understands Castilian, and I doubt comrades would give you a hard time as long as you seem to be trying a little. If you know Castilian—and especially if you also know some French—it doesn’t take long to pick up the gist of a lot of what’s said, and reading is easier still. Bona sort, camarada.
I wish I had advice as far as parties, but my time there was long ago and closer to turístic than residencial.
iirc there's Moviment Socialista (trots), the only ones I know that do something at all. Maybe PCOE?
e: Don't worry that much about Catalan, you'll learn gradually.