Not to muddy the subject, but read the manual carefully. I'd trust the owner's manual over a website on a car's basic requirements.
If it says "premium unleaded fuel only" then you should only use the 91+ octane gas. If this is the case, the fuel gauge in the car will usually have this warning label as well.
If it says "for best performance premium fuel is recommended" or similar, then you should be able to use regular 87 octane gas.
To my knowledge and reviewing the specs, the Toyota V6 used in the Camry/Solara does not require premium fuel...while a bit high, the 10.5:1 compression ratio doesn't warrant it.
Hope this helps!