One thing you have to know about is the Albrook bus station in Panama City, Panama.
It’s where all the local AND long distance buses depart from including traveling to Costa Rica.
I had a hard time finding the Albrook site because when you search in English, nothing ever shows up. Just remember to use Chrome, & it will automatically translate it from Spanish to English, assuming Google isn’t having server issues & the site is coded properly. Pretty much all the websites in Panama are terrible. Beyond poor code & terrible GUI, so that can hinder the translation process, but we make do : )
And embrace the sites that are professional & nice enough to give you the option of English or Spanish. They are rare, but they are out there.
Now you have it!