Backstory:
I'm from Argentina but live in the U.S. I spent 6 months down there recently and unfortunately fell in love (not really unfortunate, but international long distance sucks).
We are trying to plan a vacation, but no matter how many sites I search, I'm having an incredibly difficult time finding what dates will be least expensive. Even through matrix and such.
What we're trying to do:
We are working with two main options, but are flexible. The really cool idea is that we meet up in Mexico City, I'll drive down, she'll fly up. Then, we go see my friend in Xalapa and drive up the coast back to Texas, making stops at various beaches along the way.
Second plan: much simpler. She comes up to Dallas, where I meet up with her and drive to Austin (my current hometown).
Our dates are flexible, and we're looking for anywhere from late july to mid August, with her staying here for about 3 weeks.
Where can I go to find information on variable dates? Matrix has prices that are way too expensive. I have found some for $1100, which turns into $1400 after all the fees. We desperately need this to be as cheap as possible since neither one of us makes a lot of money, but airline websites (and travel websites) provide almost no information on when the fares are going to be cheapest. We're just having to guess random dates and plug them in.
Any help, advice or direction is extremely appreciated.
Edit:
A few details:
She is in Cordoba, AR, I'm in Austin, TX.
I have searched on Kayak, skyscanner, despegar, copa airlines (some of the better results through other sites, not from their main page $1400), united airlines (also half decent results, $1500 to mexico, $1400 ish to dallas), hipmunk, american airlines, lan, uh... that's all I can think of so far.
Going directly to the airline websites has provided almost no result, with the exception of united. I don't know where else I can search or how else I can search to find the best dates.
Argentina has a ridiculous 35% tax on international flights, but we're getting around that by having me pay with a U.S. credit card.