Both are possible, but the meaning is not quite the same. "don't count on me" means "don't rely/depend on me". "count me out" means "disregard/exclude me".
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for learningI would like to know, please, whether the following sentence:They are not exactly the same.
"I´m not planning to go to the restaurant, so don´t count on me", has the same meaning as:
"I´m not planning to go to the restaurant, so count me out"