World Of Warcraft: Solo and zone level

All I want to know is:
Will it be set up for a person who just wants to solo? I hear BC is going for the more casual player, am I going to be forced to join a guild in order to get good drops? Can I not enter the new world by myself?

You can do just fine in outland as a solo player, and can get to 70 just as easy as you got to lvl 60. The game is similar in all aspects, so if you want the best drops, you need to do instances, but those can be done in casual groups so not even there do you need a guild.
I would say it's more fun in a guild, but no - it's not needed as such.

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Will you be able to level in the outlands during the lower levels (1-60) or is it a 60-70 zone only?

It's a lvl 60+ zone.