Tab is great for the guitar because it makes things very easy to play without having to learn many ledger lines for the upper register as you would with notation. However, tab has some drawbacks - most importantly, it does not show rhythm. It is useful therefore to know a little at least how to read basic music so you can fill in the rhythm, rests, time signature, dynamics and so on so that you can play the music how it was intended to be played. It's also useful for a well rounded musician to know notation especially if you have to play with non guitarists.

Having said that, you could most probably get by with some theory and the usual guitarist's knowledge of chords.