Which ones will survive so that the OP can rent a car in the fall.
I've been sticking with Enterprise/National for number of years now and never had a complaint, it also helps that its what we use them for work travel and have a corporate account, which i definitely reap the benefits from. they seem to be doing pretty well, so i wouldn't worry too much.
also to the OP: you should only reserve cars directly with Car rental companies. since you don't actually pre-pay until you pick up/return the vehicle, making a reservation now even with multiple companies will cost you nothing.*(sometimes they do offer little discount if you pre-pay at the time of reservation, but given current situation i'd skip this). It's perfectly common in car rental business that those who reserved: do not show up due to missed/late flights, etc. if you're not at car rental with in 4 hr or so of your expected pick up time, your reservation is gone, and that's it. as long as you didnt pre-pay.
here are few tips when it comes to car rentals:
#1 - sing up for a free rewards/membership account, even if you dont rent often, it helps when dealing with customer service vs being a one time rental w/out an account.
-book directly with companies and not via 3rd party.
-stay away from Dollar Rental and other bottom dollar rental companies, trust me, piece of mind and ease of renting through one of the bigger companies will go a long way. Top tier rental companies will also always have newer cars with less miles. i cannot remember how many times i've gotten into a car and it had less then 100 miles on OD.
-OP start looking for rentals now. little secret: you can have multiple reservations with same company at the same time. *(sometimes i reserve different cars for different lengths of stay if i am reserving before i finalize my travel dates/book flights, then i go back and cancel the one i dont need)
-dont just focus on one specific Car Class: ex: Mid-size sedan. pricing for a lot of these companies is fluid and is based on demand vs inventory. I've gotten a mini-van cheaper then a sub-compact would have cost me. so check ALL vehicle classes.
-i usually check weekly or bi-weekly to see if rates have dropped as i get closer to my travel dates. simply try starting a new reservation search and see what the total is. if prices dropped - great make that reservation for a new lower rate, then you can go back and cancel your old pricier reservation.
-OP also if you're renting for lets say 5 or 6 days, check a weekly rental price. It can be cheaper to rent for a week vs 5 days. and while your reservation is for 1 week (7 days), you actually can return early and only get charged for # of days used. ex: 7 day rental = $700 ($100/day), if you take that rental through any of the major companies *(you can double check this with companies on your own prior to rental just to be sure), and lets say you return your vehicle on day 6 of the 7 day rental, they would only charge you for time used: aka 6 days/$600, even thought your reservation was for 7 days. ***(I've been in a situation where i flew into a major city for 1 night/1 day and needed a rental last minute upon arrival, but even with my corporate account/status, their inventory was so low, that i was told there is NO cars available for 1 day rental. so i simply made a 1 week long rental reservation on my phone car rental App right as i stood in the rental company's office, and all of a sudden car was available and they pulled it up front in matter of minutes. my coworker and i took the car, and had it returned not even 24 hours later to the same place. we were only charged for 1 day even thought we made a week long reservation to get around Inventory shortage)
-OP check with your insurance to make sure it covers your rental so you dont get pressured into buying their insurance. but be sure that you are covered. *(for my work travel i have an umbrella policy so i personally dont have to worry about it). only time i ever bought their insurance was in a different part of the world where having a car is sketchy and its likely that it will be damaged/broken into.
good luck.