Okay... while I agree with the above, I'll get back on topic, playing MMO's solo works in some games but is generally a bad idea in any kind of sandbox. There are many well established corps that will take on new players from day one so I don't think you'll have any trouble there. Most established corps (62nd, RG, M2S, CIR, etc) still recruit and train new members (the game is still young in many respects), or you might look at some of the younger corps that will have more people closer to your own level of progression, like FOOM and ATG.
I'm wondering, how quick can I take part in PvP if I start fresh? Is there some builds that are viable quicker? Thinking of group PvP. Also, are there many active PvP groups? So that there is combat to take part in?
Short answers: very quickly, yes and yes.
I might wait until the end of the first week to jump into PvP, though you could probably jump in sooner... While some people might min/max into mechs (probably under a month of EP). The quickest way to get into PvP is to go small and fast, hunt in groups and use detectors this way you control the terms of engagement. As part of a collective hunting group the only skill you will NEED is NAV 10. After that decisions can get more complex and will be role dependent, talk to whatever corp you have decided to join.
"You're living in a parallel universe." ~Syndic