Hi: I am costarrican and back in +-1965 there were 3 Peace Corps volunteers who at a given time lived in our home. They are: Kent MacDonald and Jane Purington from Massachusets, and Zeva Smith from San Francisco. I am from the south of Costa Rica (San Isidro de El General). The volunteers usually stayed at a given hotel when in San Jose, the capital city. I forgot the hotel's name. I believe it was the Metropolitano.
I was about 16. I met him there and I can never forget him because he spoke fluent Spanish (unusual among PCV's), told me he was Puerto Rican, possibly 5'6 - 5'7. He was dark but not totally black and softspoken. They called him Matt, but when he repeated his name to me he said Matias.
If you need directions to Guapiles, I'd be able to get them for you. Nowadays it's way easier than when your dad was there.
I hope to hear from you, Dimas Barrantes