There are so many plants native to Mexico it will make your head spin. Many of the plants grown in the more northern climates (US, Canada, Europe) as annuals are native to Mexico. I am in the tropical zone and i don't know where you are or what your elevation is. I would recommend bougainvillea as a spectacularly photogenic plant that is the most beautiful when neglected. Also, Ixora coccinea (not the dwarf variety) is an easy to grow plant with lovely blooms and vegetation. Plumbago is beautiful and easy to grow (depending on your climate) and there are dozens of exotic showy vines. And lets not forget Hibiscus. If i were you, i would take a walk around the local parks, take a photo of what you like and then take the photos to a good vivero near and ask if they have the plant, what is it, if it is easy to grow, etc. Many of the plants i mention above become quite large, for some smaller plants you might like some of the sages,for example, salvia coccinea is a stunner. Have fun, you will be amazed at the abundance. oh yes, and let's not forget Cosmos (grows wild, i've never seen it sold in garden centers but you can purchase seeds from the US and UK).