I'm not sure you're posting was strictly a question, more like feedback. Anyway, thanks for bringing such an important attraction as the Botanical Gardens to my attention. There is now a page dedicated to it on my site.
To be fair, you did actually ask a question regarding getting to it from Las Americas by bus. You should take the 343 express, which, as its name suggests, only makes a few stops. Get off at the Hotel Melia, after which you have a walk of about 25 minutes to get to the gardens.