Specifically with your gig, it's probably not worth it. Typically, if someone sees your band on one weekend, they need at least a month or more before they'll go out and see your band again. Knowing that, it's probably not a good idea to tick off the bar owner by telling everyone to take their money elsewhere next weekend, when you won't get much payoff by actually getting those same people and/or their word of mouth friends to your other gig.
That brings up another point... Unless you can pack the place or sell out the place your playing tonight, why book a gig so close to today? Spread your gigs out more, both geographically and time wise. Next weekend, you should be playing in the 'burbs, if tonight is in Hollywood. The week after that should be in the Beach Cities, then Orange County, etc., etc., until at least a month (better yet two or three months, if you can) go by and you hit up your first place again.