I've towed race trailers with everything from cars to bikes to racing lawn mowers all over the country. I've used a reciever hitch bumper style bike rack I made, and liked it. BUT, there is no way your car will take it. 500-700 pounds of tongue weight on my Suburban and it's bagged out. Went to air ride control on the back.
If you really don't want a trailer, get about five 100 pound bags of cement and toss em in the trunk (whip by Home Depot and see if they'll let you try it without having to buy the dang cement). I'll be the car is so bagged out that once seeing it, you wouldn't even try to mount the bike back there.
Get a trailer, you'll never go wrong, and you can use it for other stuff.