Be candid?
Okay........ I LOVE IT! The blues and greens you use in the X blend well together and allow the 'mexican tiles' to stand out beautifully. Then you've got the secondary lines of the + in the contrasting colour and the blue background fabric which separates nicely from the rest of the design. I'm not very good at explaining what I mean but I'm sure you will understand. I think this block is well thought out and a complete quilt is going to look stunning! Well done!
P.S. I would never have thought of placing the Mexican tiles the way you have. Brilliant!
P.S.S. What size did the block finish at?
Sorry, another edit! The only thing I would maybe change is the position of the Mexican tiles. The top two are brighter than the bottom two so maybe swap the top right with bottom right so that the brighter tiles are opposite each other instead of next to each other? Just a thought?