We make the journey to Florida often--and also to Colorado. Since we live in the middle I will dare to make a suggestion:
At Mobile take US highways through Alabama and Mississippi to Jackson, MS and pick up I 20. Take the loop around Shreveport (and slow down on the short rough section just before the loop.)
Watch for Exit 628 soon after entering Texas. Exit there and take US 80 to near Marshall, TX but watch for loop 390 which will take you around the town to the north--hardly a slow down. Exit the loop onto US 59 toward Texarkana, but exit at Jefferson onto TX 49.
Follow TX 49 all the way to Mount Pleasant, TX where you will pick up US 271 north to Paris Texas. Take the loop south around Paris (again no slow up) From the loop around Paris pick up US 82 West. Follow 82 all the way to Wichita Falls where you will join US 287 to Amarillo. Watch for the loop around North (it's Loop 335) to pick up US 87 N to Dumas, TX and on through Dalhart to Raton, NM where you will join I-25 on over Raton Pass into Colorado.
I know it seems complicated but it is a route with which we are familiar--every mile. Best of all it completely avoids DFW and the traffic there. US 82 follows the Red River (near the Oklahoma line) and we have found we have to go that far north to avoid Dallas/Fort Worth.