I've stayed at the smallish Hotel Marbella in the El Cangrejo district. It's nothing fancy, but it's clean and safe and you can walk around the neighborhood day or night, and that's always a big plus in Panama City. It's the type of place where a Panamanian business traveler who doesn't have a big enough expense account to stay at one of the luxury chains would stay. It's perfectly acceptable.
www.hmarbella.com
A single is $55/night, including taxes. Breakfast is not included, and Internet access costs extra.
Quite honestly, I wouldn't stay at a place that was any less. They exist, but they'd be in very dicey neighborhoods.
As a photographer, you'll go wild in the Casco Viejo, the historic center, with all the colonial architecture. The neighborhood is far removed from the business district, and you'll need to take a taxi to and from.
Panama's Independence Day is Nov. 3, before your arrival.
I'm a travel writer and, quite frankly, I find ATP, the Autoridad de Turismo de Panamá, to be pretty unhelpful. Even just trying to talk to somebody to find out what's new, what should I be covering ... They don't reply. I wouldn't count on them for any help.