I often see this phrase "count me in". If someone says "count me in", can I say "me too"?
As long as you know what it means. "I will particpate/I will be part of whatever you're talking about."
"Me too" would then mean "So will I."
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.