Have I "even" asked at local Viveros comes across as critical. I know how to drive around and ask and I also know many will say yes, and yes I have done that. That doesn't mean they can really do it or that they are reliable. After living here several years, I am not that trusting anymore. I get a lot of "yes" I can do from people and the work is shoddy.
The best way is to get a referral from someone. Also, I had a person who said he was a landscaper and yet when I asked for drawings , more than once, he never provided them and what seemed obvious to me, is that he considers himself a landscaper because he installs landscaping. That is not a landscape designer by any means.