the background looks good, but i see you tried to use fill flash to lighten the flowers, i dont think you had the flowers in focus though, so it looks a bit odd, the colors are very rich and vibrant though, so good job
A beautiful place and good idea but you need to work on the details to go all the way. The foreground cactus is to dominating in the image. It overshadows the beautiful backdrop. Try to make your foreground object more subtle. The lighting on the catus is also unatural, try using an lightweight protable reflector you can get a more naturally balanced light on your foreground subjects.
Fill flash excessive IMO (particulary with the shadow just beyond), the contrats is too strong and the color balance unnatural between the cold foreground and warm background.