I think they need to take a page from what the large casinos do to get people in the door, but on a smaller scale due to the budget.
1) Giveaways - casinos give away cars and cash, jai-alai could do electronics like flat screen TVs and GPS units. One every couple games, prizes getting better as it goes on.
2) Food - casinos are famous for food comps whether it be a buffet or fancy steakhouse. Jai-alai has nothing but bad snack bar food. Somehow get a restaurant in there who wants to promote and offer some decent food. Outback Steakhouse is always packed, bring them in....they even participate in amateur golf tournaments.
3) Drinks - of course the casinos give away alcohol (except Hard Rock!) so jai-alai needs to do a regular beer promotion. $1 beers, bucket specials, half-price wine, signature drink specials, etc. Easy to implement.
Then do the promotions you see at baseball games, even minor league. T-shirts being tossed out, contests for the fans that are fun with small prizes, give out admission passes for future performances, have 1-2 players sign autographs.
Target specific events like the UFC fights, NBA/NHL playoffs, big baseball games like Yankees/Red Sox, have a fireworks night once per week with a big event July 4th, etc.
Justifying the cost may be an issue, but people will come if they (1) know they will be entertained, (2) can have some good food/drink and (3) feel like they have a chance to win something. They want a good night out. And they need to understand what's going on - so a little education along the way from the announcer and with a booth on the game, betting etc would help.
That's it. It will take some money but can be done efficiently.
I think you promote it via mail, email, radio, website, newspaper and the programs. You measure the increased attendance/handle over a period of several months. Give it some time to get baked in so to speak.
Keep the place spotlessly clean and give them a reason to come back. No employees acting like they're doing you a favor by punching a ticket or getting you a beverage. Basic good business practices.
Here's an example. We've all been to movies where the theater goes out of the way to offer you a good experience with a vibrant lobby, better food options, things to do, etc. Then other places tear your ticket and you have to put up with a grumpy employee serving stale popcorn. And that's it. Both offer the same films, but where do you go back when you go to see your next movie? Which one is jai-alai right now?
Let's also recognize that the people in place now may have great ideas but can only do/spend what the powers at the top allow....I do understand that and they may be more frustrated than us with the way their hands are tied from a marketing standpoint....