Can anyone recommend a nice place to see sloths?

https://maps.app.goo.gl/Po8qtSszAwSR3r5JA - here you will always see one and in it's natural environment.

https://www.slothwatchingtrail.com/

Also:
https://www.google.com/maps/dir//Costa+Rica+Animal+Rescue+Center,+C.+Juntas,+Alajuela+Province,+Turr%C3%BAcares/@10.0123036,-84.5210621,12z/data=!4m9!4m8!1m0!1m5!1m1!1s0x8fa05421bd28905f:0x1927385309f8dfdf!2m2!1d-84.3469467!2d9.9411525!3e0?entry=ttu

And of course Manuel Antonio!