Absolutely it is. WoW is a very solo friendly MMORPG. To be entirely honest, soloing the whole way is the FASTEST way to level, doing quests and the like. 1-70 will go by faster in terms of hours played if you just quest your way through things. Instances generally slow you down. However, you're going to have to learn your role in a group at some point in time...and instances are one of the more fun parts of the games. So you may as well get used to playing with other people as you level, that way you're not clueless when you don't have a choice anymore.