You'll probably find that even though servers are merging, you will still find the population not over-crowded.
Almost all zones have the ability to "split zone". Meaning, if a zone get to a large capacity, another identical zone will be created. When you zone in you will be given a choice, Antonica 1, Antonica 2, etc. I remember during the first few months of the game, there were 5 Antonica zones!
This is different to the traditional instanced zone, like LDoN, where you and your party are the only ones there.
The actual numbers of the servers still seems to be a mystery. You can tell the current server load when you create your character and select a server. You could look for one with a low server load during your normal play hours. Other than that, you need to do a few commands at the keyboard, /who all fighter, /who all priest, etc. and tally up the numbers.
My guild and I have been playing on Najena since launch, and we're all in different time zones in the US. Najena has been adopted as the unofficial Aussie server, but we never have trouble finding a group. I believe there is a significant part of the population from the US also.
I typically play late evening West Coast time, so I meet my Aussie mates as they start the play-day.
Foundation is a small family guild of parents and kids that play together. We are always looking for like minded people. :) Most of our members are in the upper 40's or 50's, but we all run alts of varying levels. Our crafter has several high level artisan alts, and we are always well-equipped and fed.
Our web site is the SOE provided one, not much to it. We don't talk much on our forums, as we just take care of business in-game.
If you choose Najena, look me up. I can help you get started and we can discuss the guild. :)