If you know that verbal is a weakness and quant is a relative strength, then you should tackle the verbal right away. If you haven't already, check out bb's classic post about how to get started on the GMAT: gmat-study-plan-how-to-start-your-gmat-prep-80727.html
In his post, bb suggests starting your verbal prep in the second month, but if you're crappy at verbal, you should start working at it as soon as possible. In particular, GMAT critical reasoning and reading comprehension primarily test your ability to understand texts in a very precise, specific sort of way. If you struggle with those question types, you might just need tons and tons of practice so that you can get used to reading the dense, tricky passages that appear on the test. Yes, reading through GMAT verbal prep books can help, but there's no substitute for practicing with good, official materials.
Maybe your verbal isn't all that bad--I have no idea. But if you're scoring in the 46-51 range on your quant and your verbal score isn't strong, then it's probably time to mix in some verbal prep. Raising your quant score from a 46 to a 49 isn't terribly helpful if you score in the 20s on the verbal section. Check out the "month 2" part of bb's post, and then adapt it to suit your strengths and weaknesses. If you really are struggling with your verbal, then at least half of your time should be spent on it, since we know that your quant is on the right track. Don't completely abandon your quant studies, but there's no reason to wait to start studying verbal.
Helping students kick the GMAT in the nuts since 2002... www.gmatninja.com.