Mixing pufferfish and cichlids can be done, but not easily, and it depends a lot on the space available and the species used. In a mid to high salinity brackish aquarium, GSPs and Arothron hispidus can be combined with things like Sarotherodon melanotheron and Tilapia rendalli. A 40-cm tilapia can easily handle a 15 cm pufferfish. I've done this sort of thing with Arothron hispidus in a 200 gallon tank without problems, and in fact the dangers are more likely to come from the territorial cichlids than the pufferfish. This is especially true if the cichlids are bigger than the pufferfish. On the other hand, mixing GSPs with mild, schooling cichlids like Etroplus suratensis is a bit of a gamble. Some GSPs are fine, but others are quite nasty and will simply peck away at these harmless, even nervous, cichlids. On yet another hand, the brackish/marine tolerant Central American "Cichlasoma" such as Cichlasoma tetracanthus are also a gamble because these cichlids can be astonishingly aggressive if they decide to spawn (or at least mark off a territory).
Among the smaller puffers, I've found SAPs and red-tail pufferfish (Carinotetraodon irrubesco) to work well, though others have had different experiences. With the Carinotetraodon spp. at least, there seems to be variation depending on the collecting sites, with some populations being mild and harmless, while others are aggressive fin-nippers. Personally, my own Carinotetraodon irrubesco seem to have an "armed truce" with the Pelvicachromis taeniatus they share a 40-odd gallon tank with. The males of the two species seem to ignore each another, but strangely enough the female cichlid persistently bites the female pufferfish when they bump into one another. There is some competition for nesting sites, and one fish will chase another one out of a favoured coconut shell or bogwood cave, with the cichlids doing the chasing, and the pufferfish doing moving out! Most of the time though they get along fine, and the two species feed on different things so there isn't any confrontation there.
SAPs largely ignore fish at the bottom of the tank and rarely swim into thickly planted areas, so dividing a tank into open areas with a strong water current (which the SAPs like) and then making another area with lots of caves and roots (for the cichlids) would probably minimise any problems. When I had a pair of rams, they had no problems chasing off SAPs, and the two Pelvicachromis taeniatus don't seem to be bothered by them much either.
As a general rule though, as Fella says above, there really isn't a 100% safe approach to mixing freshwater pufferfish with anything much. In brackish and marine tanks things are easier because many species seem to be much milder in temperament (I assume because marine puffers don't make territories or guard their eggs). But I have found some combinations that seem to work for me, and provided you have a back-up plan for if either species gets in trouble, it's certainly something worth experimenting with.
Cheers, Neale