Do you guys think it would be too late to sign up for an AMEX card and get in on this deal? Assuming I have good enough credit that is. If not what is the best or fastest way to sign up?
I don't know if it is too late to signup and participate in the promotion, but I doubt it. You should definitely signup ASAP. IIRC they call you a couple of minutes after you apply to tell you whether you are going to be approved or not, and you'll get your card within the week. Also, you get at least $100 cashback after you spend your first $1,000 using the card (you have like 3 months to spend the $1000).
I use 3 cashback credit cards, the AMEX Blue Cash, Discover More, and Chase Freedom. Both the Discover and Chase have rotating 5% cashback categories, so I always use those before AMEX for the eligible purchases. AMEX is great the rest of the year for gas and groceries, when Chase and Discover aren't offering 5% cashback for those categories. The other card I could get to earn even more cashback would be the Capital One Cash Rewards MasterCard that Jimmy Fallon advertises. You get 1.5% cashback on all purchases using that card rather than the base 1.0% cashback Discover, Chase, and AMEX offer.