I'm not the most creative, but I think you are right on the food ideas. If there is little or no good Mexican food, maybe highlighting the availability of Mexican food. Maybe also have friends or family take samples outside and on adjoining streets to entice passers-by. Are there expat communities or businesses nearby? Maybe host a luncheon for one of the businesses, with lots of colorful flyers with the bar's name, address, and hours. The flyers could offer a buy-one-get-one-free upon presentation at the bar. If there is an expat building or community, maybe offer a special happy hour for the residents.
I don't know how folks from different countries are enticed, but Americans want "deals". For example, JC Penney, one of the oldest retailers, has been floundering for a long time. A new CEO came in and did a big change -- "fair and square pricing". They eliminated all sales, coupons, etc. and lowered the regular prices. The new lower prices were often as low or lower than they were with the old coupons and sales. However, people stayed away, and it went out the window quickly, in favor of more sales and coupons to bring down the artificially high prices. If Americans think they are getting a "deal", they're more apt to try it. That was a long-winded way of suggesting some sort of get-to-know us special if there are lots of American expats.
I wish your friends the best of luck. I am not gutsy enough to go it on my own.
In the voice of some comedian on a 90's sitcom: "Can Donald Trump BE any more tone deaf?" "... so amazing! NEVER FORGET"
In other news, not at all sympathetic to the man crushed by the elephant he killed.