<shrug>
Lots of great rhythm players and songwriters can't play a lead. I mean, I suppose if you really WANT to be a lead player, it's a good idea; however, I wouldn't do it just because you feel you need to prove anything to anybody.
I'm not much of a lead player, either, though I guess when I step back and look, I'm better than some lead guitarists in some bands, so I can't be absolutely horrible.
Therefore, I don't know how much my opinion will count, but I basically learned patterns at first. That got me confident enough and gave me a "crutch" to fall back on when my solos started to flounder, so that I could say, "Shoot, I'm losing it... well, back to the box." After a while, I learned box shapes all around the neck, and now I don't really need to stick to just one box anymore and the fretboard is pretty open to me as long as I stick to certain keys.
If all you want to do is play the occasional lead and be able to jam, just learn some boxes. <chuckle>
On the other hand, there are better ways. It'll bear more fruit, if you ask me, to get actual lessons from an actual teacher who can show you not only boxes (I think most of us have to admit that we use them) but also proper theory, and they'll (if they're a good teacher at least) get you to identify notes across your whole fretboard.
I'm very limited by knowing, "OK, this is where I can put my fingers while playing in E" but NOT knowing, "OK, this is where the G is, so I can flat the G to take this into a different modal direction" or whatnot. I'm a pretty generic lead player, that's for sure, and I think formal lessons would be handy.
Greg