What Brockway said.
Basically no. Now you could have some labs by themselves in there....or a pair of convicts but nothing else.
Some people don't care for the lakes to be mixed, some do. Usually temperment and water needs comes into this.
I'd take a pair of kenyi over a pair of convicts anyday in a fight. I think Africans are much more territorial and arn't scared to bull rush the trespasser. And well being a more timed african, the labs are the ones that would go down first.
So for this tank size and aggression say no.
Many other options for cichlids for a 29gal though. I'd say first decide weather you want Africans or SA/CA.
Suggestions:
Africans
Shelldwellers - You could make a cool colony of shellies.
Kribs - a pretty popular and colorful cichlid, pretty mild mannered, pretty easy to breed.
Brichardi - Lake tang cichlid (lake where prob the coolest cichlids behavior wise come from). Pretty mild mannered, especially towards their own kind. Easy breeders.
Yellow Labs - Good, mild mannered african from lake malawi with good color. A poster fish of the aquarium hobby today, and on of, if not the most recongnized fish in the hobby. You could keep some in a 29gal....i do it. I have 6 in the 29gal. You might end up having to move them out when they get larger, but they should be fine for a while.
Calvus, or Altolamprologus compressiceps - Awesome fish. Lake tang cichlid, a natural predetor....even has the looks of it. Its really rather peacful despite its looks. You could keep a few in a 29gal. They are very slow growers...just like most Lake Tang cichlids.
Julies - Cool, but territorial. They stay fairly small.
SA/CA
Rams - Good looking small cichlid, especially for a planted tank. Mild mannered. Sensitive to bad water conditions. Fairly hard to breed (at least from what i've heard.....conditions gotta be good)
Apistogrammas - Very cool dwarf cichlid. Lots of colors and look great in a planted tank. Some species are fairly easy to breed and keep while others are more sensitive to bad water and harder to breed.
Convicts - The jackrabbits of the aquarium, give them water and they will breed....i promise. Cool cichlid, lots of personality but can get testy a lot. I'd classify them as aggressive.
Keyhole - interesting little cichlid, rather peaceful. Pretty good community tank cichlid.
Angelfish - Breeding pair would work fine in a 29gal, prob. alone.
Hope that gives you some ideas. Just because you can't get the fish you originally wanted to, doesn't mean there is no chance for cichlids. Don't turn back to the darkside (community fish) for the answers!