Marks is NOT good on a weeknight to meet females, trust me, i've been several times and all 3 have been low in numbers.
The Beaches is your best bet on the Thursday night, it'll be packed.
Go to The Ritz, Brix, & Fin McCools (all with-in walking distance from eachother) and you'll be set.
Depends on the kind of girls your looking for I guess. There always tends to be a very well mixed crowd at Dive & Marks on their Tuesday nights. Wednesday I would have to say I prefer Square One. The have recently revamped the upstairs so even if your not into the dance scene there is a nice lounge with several pool tables upstairs. Thursdays are their bike night now, so yes it's mainly guys. Which by the way was a great turn out specially for their first. So if you missed out this past week we hope to see you this Thursday. ANY bike is welcome!