No, it is not normal English. I for one would say it is grammatically incorrect but that is because I take a broad view of what "grammatical" means in line with modern linguistics; however, if your position is that there is nothing in your phrase that is clearly ruled out by say, the grammar you have been using to prepare for your high school exam, then OK, let us say that it is grammatically admissible in a narrow sense of the term.
Even more than any accent you might have, usage such as this immediately gives you away as a non-native speaker. If the (lofty, admirable) goal is not to utter sentences that would sound odd to the ear of a native speaker, then this is one to avoid.
Why not? my foreign students always ask, hoping for the Grand Rule that will finally unlock the English language for them.
Well, I eat grapes indicates a habit (here: a taste for grapes): if you offer them, I will not turn them down, and it will be the same next week or next year. I am excited on the other hand tends to refer to the matter at hand, a passing affliction that we are living through as of this moment.
The two don't quite match, and that's what sounds "off" about your phrase.
(But wait, I hear you object, this mismatch is a semantic matter, whereas I was asking about syntax. That's what I meant about a broad view of grammar just now: syntax often shades into semantics, especially in a context-sensitive language such as English.)
Whenever I hear "I am (so) excited to" I can be 99% sure the next word is going to be "be" and 80% sure the very next one is "here" - otherwise it will almost always be some present continuous form. So:
I am so excited to be eating grapes.
Is good English. But you will still sound like a martian, because the normal thing to say is something along the lines of:
I just love these grapes.
These grapes are really good.
You got grapes? They're my favourite! Can I have some?
Final tip: forget about grammar. Focus instead on stock phrases.