NO SE DICE: "COUNT WITH YOU"
This is an interesting one, but it is also challenging to rewire your brain so that you stop making this mistake! This expression is useful in a business context but also when you are socialising with friends, so it is well worth remembering. The source of the problem comes from the Spanish phrase: "Cuento contigo"!!!
Considering the Spanish form, it is absolutely natural for Spanish speakers to say "I going to count with you". The problem here is that if I, as a native speaker, here that phrase the first thing that comes to my mind is that someone is going to count numbers with me: "one...one" "two...two". Do you understand what I am trying to say?
The correct version here is to use: "I am counting ON you to help me with the preparations for the party".
Hope that helps!
Soy el director de Daniel Smith + Partners. Tengo más de 10 años de experiencia enseñando inglés a españoles.