Karen,
I would take the time to do a mini lesson on adjectives now. With 2nd graders, you can teach them the power pix for adjective using the 5-step lesson plan on the power pix file. Once they have a gesture and some basic knowledge, you can continue to build on it every time you write a spicy sentence.
I teach 5th grade and my class is 95% EL's, to make sure they didn't forget what an adjective is I wrote this on my white borad "Adjective- describes a noun." Also, before we write a spicy sentence I always ask "What is an adjective" to which they all reply "An adjective describes a noun" (with gestures).
The other thing I would suggest is practice, practice, practice. It sounds like they already know how to replace the noun in the blah sentences. How about writing a blah sentence (ie: The dog sat.) then add the spicy sentence like this The ________ dog sat. (label the blank adjective) and have them talk with their partner about all the adjectives they can think of (the sillier the better) to describe the dog. This will get them thinking about the process.
Let us know how it goes!
Tiffany
WBT Intern, 2011-2012