I've spent the past 8 days in Costa Rica and have found the service pretty decent. My experience was limited to Liberia and the Guanacaste province so I can't speak to the rest of the country. My phone was on kölbi & Movistar for about equal amounts of time. It also parked on Claro, but for a much lesser amount of time than the other two. Being able to access all three networks meant that coverage was excellent. I don't recall a time that I saw 'No Service', but to be fair I never went all that deep into any rain forests. If memory serves, I was accessing B7 LTE with kölbi, B3 LTE with Movistar and W-CDMA with Claro. Speeds were typical of Sprint's free slow data 0.02-0.03 Mbps and pings a little above 350 Ms.