Are vowels most often pronounced long or short?
Solution 1:
There are several problems with your question. the first is that you have not correctly identified the short and long vowels. I have tried to do this for you below. As you have mentioned non linguists, I have not used phonetic symbols. Please note that the vowels and diphthongs I have listed are those of standard southern British English.
Monophthongs
bad - short; bard - long;
bed - short
bid - short; bead - long;
bod - short; bawd - long
bud - short; booed - long
put - short
about - shot; bird - long
Diphthongs
bayed; bide; buoyed; crowd; abode; beard; bared; boor.