I'm not sure if they would be 'balanced' with most of the core races, but they'd be far, far below any properly designed LA +1 race.
If I were going to do this (which I wouldn't, since the -2 Con fits my view of elves outside of Dark Sun), I'd probably lose the fiddly 4 hour meditation and secret doors abilities.
EDIT: The more I think about it, the more I think this would probably be a good mechanical change. As it stands, elves suck; they're perhaps better than half-elves (although -2 Con hurts more than any other stat) and certainly better than half-orcs, but they're trash next to gnomes, halflings, dwarves and humans. My chief concern would be that, with +2 Dex and free weapon proficiencies, elves would be better than they should be in fighting roles. Perhaps dropping the proficiencies down to familiarity (with the elven thinblade and greatbow, perhaps?), and losing the two fiddly abilities mentioned above.