If I'm talking with a friend that is a few years older than me should I use the 요 form for verbs or should I use the completely informal speech?
I'm going to interpret your question as "do native speakers use 요 with friends who are a few years older than them?".
The answer is "it varies". It depends on lots of different factors. I'll give a few of the most common factors involved, very rough order of importance, it really much differs from person to person and situation to situation so do not take it as universally applicable, there's no "correct" answer here.
- Size of the age gap
- Degree of closeness/How long you've known each other
- Personalities of each person involved
- The age of each person (2 years difference likely feels different to an 18 year old than to a 60 year old)
- Where you first met each other
As for your situation, you've only told us the 1st factor (and even then not accurately) so it's difficult to give practical advice. In general if the person you're talking to is fluent, it's easiest to just use 요 until they mention lowering your speech and from that point start dropping it.