My daughter just told me her 7th birthday "FIESTA" was "the best ever!".... On the internet, I found a Fiesta themed picture I copied onto the front of her invitations.  Inside, I wrote "Arriba, Arriba!  We're havin' a FIESTA to celebrate ______'s 7th birthday... Hope you'll join us for tacos, nachos, and a pinata, too.... it won't be as HOT HOT HOT without you!  I tried to keep invites to about 7, but she talked me into 12 of her "best friends"!  We decorated with Fiesta balloons (watch for Cinco De Mayo sales) and some cute fiesta decos from a local party store. When they arrived, the birthday girl greeted them wearing her sombrero and invited them to make their own tacos - I also made kids sangria punch, for which you can also find recipes on the web. I ordered maracas from Oriental Trading and gave each child a pair to keep. Internet research provided plenty of Mexican game ideas - search for "Cinco de Mayo". We played Benito Juarez says (like Simon Says) and did a Mexican hat dance (a niece brought a cd with lots of GREAT music for the occasion - La Bamba, the Macarena, Feelin' HOT, HOT, HOT, etc..). Then we had the pinata.  I found that children this age LOVE pinatas. Favors?  Easy... I just gave them each a brown bag to hold their pinata fillers and maracas... THEY LOVED IT! Then we opened presents and had cake.  A local grocery store printed front of invitations on top of the cake and wrote Feliz Cumpleanos, _____.  (Happy Birthday in Spanish).  I taught the kids how to sing Happy Birthday in Spanish (very easy), so they did it first in Spanish, and then again in English. This was an inexpensive party that delighted kids AND their parents.