Relax take a deep breath you have nothing to worry about.... You can easily get a taxi to either place. Going from RIU to CoCo and you want to walk get a ride to cosmo's and start there, it's a nice leisurely walk to CoCo from there and there's a lot to do and see on the way.
Oct. is slow season but most everything is open on the beach.....As far as weather is concerned Oct is rainy and hurricane season, that being said just expect
that there might be an afternoon shower but I'm sure the whole trip won't be a rain-out. If it does shower it clears up right after that and is a welcome reprise
from the heat....Atmosphere might be a little slow but still fun, I would worry about that.