An initial "Hi" is just fine by me, it's what comes after that is of importance. Are you a male avatar? If so, general consensus is that people PM you less than if you are a female avatar. In any case, you probably won't be overflowing with PMs initially so don't be concerned. If you find a room with local chat and you are comfortable joining in, go for it, as local chatters are generally very appreciative and will generally be welcoming if you are new.