I have never gotten glue on my iron when elmering (as my friend calls it). I use a diluted glue--maybe 1/3 water to 2/3 glue. But it wasn't even a problem when I used all glue--diluting it just makes it flow easier. Does your glue go through the fabric? Maybe you're using too much glue?
When my iron plate does get gooey I clean it easily by rubbing it on a dryer sheet when the iron is hot.