You can't bring any citrus or citrus relatives across the border. Its been years since I've made that drive so I don't know how they inspect but I do know the fines are high and they don't play around when it comes to the citrus industry.

I'd recommend you do all your shopping on the way home.
I cannot imagine trying to vacation and keep your plant purchases in good shape between hot car and cool hotel rooms.
But you could stop on the way down, get the business cards and arrange purchase and shipping once you get home.

Woops,that was top of my list John (a lemon tree),thanks you guys are awesome:)