Dfyjkt

I'm an Australian citizen travelling to the US (first time) in early December. .. I will be sightseeing and visiting friends in the Washington DC and NY area. I will be arriving on December 2nd (can't change this)...

Now there is an event I badly want to attend on March 10th which unfortunately is after my 90 days are up. I am thinking about flying to Mexico or somewhere chilled at the end of February (my latest engagement is February 26th) and then re applying for another waiver once in Mexico. Then I would fly to Atlanta on March 9th and stay for the event which ends on March 13th after which I would fly home to Australia.

So I know that I would be attempting to re enter the US really soon after my first 90 days (like a week in Mexico), but I would be able to show proof of my intended return to Australia (my partner is waiting for me, university semester has begun, etc).

Is there anything theoretically wrong with my proposal and do you think the immigration officers would likely let me back in? As I said, I am only doing this to stay for 1 weekend and then flying home.

--- EDIT: FURTHER QUESTIONS ---

Thanks everyone for your very helpful advice.

So in terms of being let in on the initial visit (early December), would a flight to Mexico not count as an exit flight out of the US? I mean, surely lots of people buy a 1 way ticket to Mexico (or surrounding countries) with the intention of backpacking for however long they can manage.

Ie. say I get granted my ESTA and book a ticket from AUS-US on 2nd Dec and another ticket from US-MEX on 26th Feb, with no further plans at that time (I want some sun and sand after a cold US winter, and I don't have to be back in Australia until some time in March.

Then once I am in the US, say sometime in January, I decide I want to go for it and book my ticket to the event in March and also book flights from MEX-US on, say 10th March and a final flight from US-AUS on 13th March.

Would it then be safe to say that my initial entry in December wouldn't arouse any suspicion (as I have a flight to Mexico within 90 days)?

God I hate bureaucracy!

PS: At this stage unfortunately I am not able to apply for a B1/B2 visa because of time constraints. I have to wait 3 weeks for my new passport to arrive and I leave in 6 weeks :/

Going to Mexico won't reset your VWP counter, you'd have to go a little farther than that for this to happen. However, given your entries are more than 90 days apart (97) there's no need to reset it.

If you are admitted to the United States under the VWP, you may take a
short trip to Canada, Mexico, or a nearby island and generally be
readmitted to the United States under the VWP for the remainder of the
original 90 days granted upon your initial arrival in the United
States. Therefore, the length of time of your total stay, including
the short trip, must be 90 days or less

That said, as others have pointed out, admission under VWP is always at the discretion of the border official. While technically there's nothing stopping you from trying to re-enter shortly after your 90 days, expect some questions about that. Having proof of returning to Australia and some strong ties will definitely help your case.

It seems that your most likely problem is going to be applying for entry just two weeks after having spent 87 days in the US on the visa waiver program. Since you will be asking for a four-day admission, and will have a ticket to support your assertion that you plan to leave after four days, this is unlikely to be a huge problem. You'll probably be fine.

If probably isn't enough certainty for you, you can (as noted elsewhere) apply for a visitor visa (usually a combined B-1/B-2 visa). When you enter the US in B-1 or B-2 status, you will generally be admitted for six months. This will save you from having to leave the US between your December trip and the March event. The visa fee is USD 160.

There are a couple of possible solutions.

You could use the Mexico idea, but substituting somewhere more distant for Mexico.

The other option is to apply for a visitor visa. It costs money, and requires an interview, but normally results in admission for six months. You would need to check interview availability to see if you have time before your travel.

For both these ideas, evidence of strong long term ties to your home country and a reasonable a short term travel plan in the US is likely to be helpful.