I pretty much quest to level.

My focus this expansion has been on PvP (as it was since Ulduar was the top raid, in WotLK).
I've not set foot in any Cataclysm instance, actually.

I found with Aquatic Form and the minor glyph for faster swimming...
The water zone (Vashj'ir) was actually quite fun, with a neat story line.
All my other teams, lacking instant cast swim speeds... despised the zone, and actually ended up skipping it.




Instances are definitely an option.
And with all of the relevant quests, right at zone in, your first successful run should be close to a full level.

You can also do PvP, especially if you're x4 in the x0-x4 bracket or x9 in the x5-x9 bracket for your BG.
Solo boxing at maximum level is quite strong; multi-boxing at maximum level is more so.

Both are options, if questing gets too monotonous.
As is bouncing between teams, and only playing with rested experience for double experience.