My seats don't fold down either on my 2001 Mitsubuishi Galant, which is just stupid.
When I first started riding, I used my Saris rack to get to rides, but I never really liked using it and I didn't like leaving the bike on the rack unattended and exposed to the elements, which made going to rides straight from work difficult. I figured out that I could slip the bike in behind the front seats. I have to take the front wheel off and turn the fork sideways, but it otherwise fits.
It's a 50 cm road bike; it it were any bigger I doubt it would work. I use a velcro strap to hold the bike in place behind the driver's seat. Granted, it has scuffed up the back a bit from the crank and chain, but given that I plan to keep the car indefinitely, I don't worry about it all that much.
Unfortunately, I'm now parking in a new parking garage (my old garage was a secure government lot that's now under construction). I don't feel comfortable leaving my bike in the car where you can see it so my riding habits after work have changed somewhat. I can get it in the trunk if I take both wheels off, but that's kind of a PITA.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher