Mulder and Wolf are front line studs and should be starter everywhere except Coors. You don't play matchups with these guys.
Lohse and Willis are guys that you would want to play matchups with but they are both facing weak teams, so I'd start them. Franklin has looked good lately and he's pitching in a pitcher's park, but the Angels have been playing much better lately so he's more risky than the other four. I'd probably start him anyway.
The two that you want to avoid using are Lilly and Chacon. Lilly has been just too inconsistent this year to trust against the Rangers' potent offense. Balls have been flying out of Alameda County Colliseum this year, and his last start Lilly gave up 5 homers to the Braves. Propensity to give up homers spells disaster when you're facing the likes of ARod, JuanGone, Palmiero and Everett.
Chacon is another guy that I wouldn't even have on a roster let alone start. Being a Colorado pitcher, his propensity to get lit up like a Christmas tree is just too dangerous, and he has been inconsistent this year with no rhyme or reason as to how he performs. He has been both brilliant and brutal at Coors and on the road at times. Looking at his last start at Coors, you probably would think that KC is a favorable matchup even at Coors but he went on to give up 12 earned runs. I realize SD is a weak team and it's tempting to start him, but that's just playing Russian Roulette. Never start any pitcher, especially one as inconsistent and marginal as Chacon at Coors. In fact, I'd just dump Chacon outright if you can't get any trade value for him.
In short, I would start Wolf, Mulder, Lohse, Willis and Franklin and bench Lilly and Chacon.