During our month stay in Isla Verde, we found that many taxi cab drivers did not adhere to the published fares listed in the tourist guides. Prices are supposedly a set rate determined by travel within specific zones. Most drivers did adhere to the guide but others charged between $2-4 more. There are no metered taxi cabs. During one awful experience, the driver wanted $25 for an $18 fare. When my husband complained that we were being cheated , and would complain to the taxi commission, the driver became abusive. Ultimately, the police came and resolved the issue.
So, if you are taking a taxi, confirm the price before getting in the cab, and be assertive that you know the correct fare. Don't be taken advantage of while on vacation.