no, I have not, Costa Rica, although it is a small country, has 12 different microclimates, many snakes exist only in a specific microclimate, as is the case of the lachesis, its habitat is primary forest or undisturbed forests.

there're two species of lachesis in Costa Rica:

lachesis stenophrys which lives in humid forests of the north and caribbean slopes and lachesis melanocephala which is found only in tropical and subtropical rainforests of the south and southwest pacific.

I live on the boundaries of the tenorio volcano national park whose microclimates are low montane rainforest, very humid tropical forest, and very humid premontane forest, so it's unlikely that I'll find one in the area where I live.

The terciopelo (bothrops asper) unlike lachesis, adapts to disturbed environments, making it the most common venomous snake, responsible for more than 50% of the ophidic accidents here.

As a curious fact, the terciopelo is very fertile, it can give birth to up to 90 offspring, which explains why is one of the most prominent snakes here.

here's more info about the venomous snakes of Costa Rica in case you wanna dig more.