"I go" would be "chodzę", this doesn't seem to be a timetable after all.
"I'll go" must be a remnant of the old policy of not caring about the tense mix-up. Removed.
The current policy is to crush English into a Polish native speaker's vision of English as a form of Polish. It is not, and in practice we sound like foriegners who cannot speak Polish properly because we are in fact still speaking English with foriegn words.
Word order seems ok. However, idę is an alternative of pójdę here. It implies an imminent future action. So only I'll go and I'm going are correct translations. But only I'm going is accepted to avoid confusion, because I'll go is a totally different tense than in the Polish sentence.
Thank you! That makes sense. "I go" sounds habitual, when this is referring to a one time action, if I understand correctly.