How many low level players are around really depends on time of day, and if there are a lot of new players, or people working on alts running around. Usually you can find a few people to group up with in the levels easily, although you may need to do a / all 1 10 or whatever level range you happen to be in at the time and send a /tell to get a group formed.
Other then that, remember that /ooc is global here, you can use it to advertise that you are LFG and can generally find people interested that way as well.
How long you need to solo really depends on who happens to be on at the time, if you see the server population is between 100-200+ there will be a better chance of seeing someone in your level range, if it's a bit early and the population is around 70 or less, odds you struggle to find people in your range, but there is always a chance a few of them are starting out new characters as well.