Can't say about hoseback riding, but for golf you just need to pay greens fees, cart, etc. Don't have to be a guest or have day pass. Guests are given preference for tee times though.
.......like most places.......has special rates for Dominicans and "residents" of the DR.......you need a cedula............... MAKE SURE YOU INQUIRE REGARDING THESE RATES IF YOU QUALIFY......USUALLY ONLY ONE MEMBER OF THE PARTY NEEDS TO QUALIFY... If I remember correctly the last time we were at Casa de Campo the discount was almost 50 percent.