Spanish is my SO's first language. She's from Puerto Rico. I am learning Spanish, focusing on Spain Spanish, which is different, no doubt. That said, in our experience, people are pretty tolerant of different accents, etc. There are quite a few people from South America living in Spain.

Language is definitely a big thing for me. Mainly because I want to speak the language. Less because I'm worried about how I'll be received. I'm not sure I'd want to be friends with someone who holds how I speak against me (especially when I'm trying). But I get the sense that this isn't even close to the prevailing attitude.