Choi hasn't hit lefties much, but he hasn't been given much of a chance either. With former managers Dusty Baker and Jack McKeon, Choi didn't get the opportunity to face many lefties.
2003 (vs. lefties): 17 at-bats, .059/.360/.118, .478 OPS
2004 (vs. lefties): 31 at-bats, .194/.286/.323, .609 OPS
Maybe if he gets more at-bats against lefties, he'll learn to hit them better. At least they should give him more of a chance than Dusty or Jack did. If he proves he can't hit lefties, the Dodgers will have to find a platoon partner.
As for Charles Johnson, he had a huge home/road split in 2003 but he's been nearly the same hitter home/away this season:
home: 118 at-bats, 23 r, 6 hr, 22 rbi, .246/.375/.466
away: 126 at-bats, 15 r, 5 hr, 19 rbi, .262/.345/.468
Roger Angell: I was talking with Bob Gibson and I said: 'Are you always this competitive?' He said: 'Oh, I think so. I got a three-year old daughter, and I've played about 500 games of tic-tac-toe with her and she hasn't beat me yet.'