I would agree with what has been said. I came back to WoW after a break to join the PCG guild (over a year ago now) but set up a new char as a trial first, before transferring my mains over. It allows you to get an idea of the guild, the type of activities we run, how many people are also levelling etc.
We are a pretty friendly bunch and I don't think I have ever logged online to find no one else around, so we are pretty busy. We are not specific, like many guilds, we look at all aspects of WoW from hard core raiding to PvP with some RP thrown in. Your concern for RP is not an issue, we have a few players who like to join in and we occassionaly hold some events but generally we run around, as you would on any other server. We do however, have the rule that you will respect all RP on the server, as we are afterall on an RP server.
It's a great guild to be in, whatever your interest in WoW and the members are all very helpful and will answer any questions whether class/quest/raid related, someone normally has an answer. As for grinding raids, sometimes you are lucky and people happen to also be looking for a group or a higher level will be grinding rep with them. The other day I spotted in guild chat that someone was offering boosts through a raid because they needed to run it anyway and were willing to take lower levels with them. There are some days when everyone seems to be busy, but you will get that in all guilds.