Is it possible to get decent at guitar in one summer?

It has always been my dream to play guitar, but I only have access to one of my siblings' when i'm home from college. I will be home for about 4 months over the summer, and I want to learn some skill in that time, and I think this would be a really great one. I've played instruments before; I can sort of play a little piano but I'm not that into it, and I've played flute, oboe, sax, and piccolo at varying skill levels, but never any string instrument. I was just wondering, is it possible to get past that initial "frustration" phase in 4 months or less? If I can get there by the end of the summer, I would consider buying a guitar to take to school so I don't lose the skill, but I don't want to spend a whole summer on it only to lose it when I get back to school. Any tips? (Also, I want to teach myself without spending a lot).