Just about the only thing you can do to speed up the skill switching process is to right click on the skill you'd like to change. By doing this you'll jump directly to the skill selection for that key, bypassing one page of the menus you'd normally click through.

This is the only way to speed up the process of changing skills. There is no other way to automate or hotkey skill selection in Diablo 3. It must be done through this menu.

Any 'out of the box solution' would require, at a minimum, the use of some form of third party macro or automation software, a clear violation of Diablo III's Terms of Use. While such violations are not always detectable or acted on, the possibility of action against your account and revocation of your license to play would give me extreme pause in considering any other solution.

If you have limited time to play and will not be online when your friends are, I recommend you play solo, at least for Normal difficulty. As Rachel mentioned, it is just as viable (until you get to very high difficulty), you will get XP and loot at the same pace, and also you may find it more fun:

• You get to play with followers (unavailable in co-op play)
• You can choose your follower and equip/spec them to complement your play style
• Followers have interesting lore and great voice-acting
• Follower AI is likely to be better than most of the random people on Battle.net
• You can complete quests at your own pace
• You can listen to dialogue and watch cinematics without people interrupting them
• Solo gameplay is arguably more tactical and strategic as opposed to mindless click-spamming

Overall I feel that Blizzard has really invested a lot into the RPG elements of this Action-RPG, and if you play solo, you may enjoy them a lot.