First off, you're screwed if you have dial up. You cannot play WoW in any significant way unless you upgrade your connection. Since I doubt you can do that though, you really can't be helped in that department
Don't play alliance just because the majority plays it. If you like the alliance races, go alliance. If you like horde, go horde. I started off alliance because I liked the look of the characters more but all of my friends played horde and I felt alone so I switched to horde after a while. There will be people to talk to on both sides so there is no wrong choice
And that goes for classes as well. Do you want to heal, dps, or tank? If you want to dps, do you want to be ranged or melee? Considering you only do 10 day trials, it would make sense for you to go dps because you'll be able to level easier and see more
If you want armor but like spells, then pally or shaman for you. Pally can dps, heal, or tank so you're not restricted to one choice. And shaman can be ranged or melee dps, depending on what you spec into