Hello Hoxiekane,
Welcome to the community!
What plan type do you have? While most post-paid plans would already be enrolled in Fido Roam, it should be noted that Basic plans do not allow for roaming. If you did not wish to avail of Fido Roam, you would need to opt-out of the service. In doing so, roaming usage would be on a pay-per-use basis. You can view those rates here.
If you have pre-paid services, you should note that roaming data does not appear to be available in that region.
You should also note that access to your Fido services would be limited by the cellular networks in Costa Rica. You would need to ensure your device is compatible with the networks in that Country. You can view their compatible bands/frequencies here.
For completeness sake, it should be noted that while using Wifi for regular internet access will not incur Fido Roam charges, there seems to be some misunderstanding regarding Wifi-calling. I'm not sure how people have gotten the impression that Wifi-calling does not use the networks. However, that is not true. While the calls and messages do not transmit via cellular towers, they still use the networks via the internet gateway (see image here). The cellular towers and Wifi are merely alternate means of accessing the networks. Calls and messages would not be able to complete or get sent/received without the networks. As such, using Wifi-calling is technically using Fido services. However, they have allowed certain usage to be free from additional charges. All the messages and calls you receive (from anywhere in the world) will be taken from your plan's voice minutes and messaging limits. As well, all Wifi-calling messages and calls you make to a Canadian phone number while abroad won't incur long-distance or roaming charges (see link above).
Hope this helps 😀
Cheers
