If you are visiting Jaco Beach you are probably doing it to look for girls. Note that prostitution is not legal in Costa Rica but it is also not enforced as illegal. This means you will find all the girls you could possible want in Jaco. The two places to go are Hotel Cocel and Beatle Bar. Hotel Cocel is full of girls that are not shy about offering you services. You can be in and out in less than 30 minutes if that is your goal. You can also spend time in the casino, at the bar or at the restaurant just getting to know some of the girls.
Note that the casino is not like a Las Vegas casino. It is not even like an Indian casino. It is basically two small video poker and slots rooms with about 5-10 tables. When I was there during the Covid Pandemic in April 2021 the tables were covered and there were no dealers. If you really want to enjoy a casino experience with girls you cannot expect to find it in Costa Rica. Go to Las Vegas.
Even if you are shy, you will have no problems getting attention from the girls in Jaco. They are very aggressive and will approach you. They are not only local, Costa Rican girls. They are girls from everywhere that know there is money in the beach town because of surfing, fishing and golf.