Perfect 5 Minute Restaurant Salsa

So good and only takes 5 minutes to make!

Warning!  Very spicy- use less peppers if you don't want the kick!

You will need:

3 cans whole peeled tomatoes
garlic salt
6 serrano peppers
fresh cilantro

1) pull stems off serrano peppers and microwave (all at once) until they pop (usually about 2 min)
2) add juice from two cans of tomatoes to blender
3) add cilantro leaves (most of one bushel), garlic salt (as much as you'd like) -I think I use 1-2 tsp, and  
    microwaved peppers to blender
4) blend
5) add the remaining can and tomatoes from first two cans
6) blend

Tips:
1) you can use salt and garlic instead of garlic salt
2) I like to get pre-chopped cilantro from the produce department.  I blend half in with the salsa and stir
    the second half in for a bit more cilantro flavor.
3) Some people have added onion, lime and traded out one can of tomatoes for Rotel.  All are good changes, but I prefer it prepared as above.

Question:

Does anyone have any tricks to picking really spicy serrano peppers?  I have tried more ripe, less ripe, larger ones. smaller ones and I don't see a pattern.