Within the Tzelman colonies, sexuality and gender preference take a backseat to class issues in almost every situation. Classes are rigidly enforced. Views of non-heterosexual pairings also fall into class spheres.
In the upper classes, it's almost expected that everyone has a marriage and a relationship on the side. These affairs may be of any gender though there is some stigma to same-sex marriage, since most upper class members are concerned with continuing on the family line.
Middle and lower classes expect partners to be faithful (as an affair is a drain on resources - it's said that only the rich can pay for two relationships or more at once). Most pressure for heterosexuality comes from continuing family lines, if there is a middle class family making a bid into the upper class. However this force is really only exerted towards only children, which is a rare occurance. Most families are quite large, and 2 is seen as the minimum.
In the Wilds, homosexual relationships (as it is mainly men who go to the Wilds) are seen as a smart move. Women whose married husbands go off into the Wilds may actually advocate that their husband have an affair with another man, as the only other outlet are prostitutes (which are often company-sponsored, incurring more debt a person has to work off, as well as riddled with STDs which are expensive to treat). Most if not all of the social stigma is removed in such situations, though pin-up girls and other pornography of heterosexual nature are highly coveted items as well.
Sex is seen as a basic need, though one that is often not discussed. Contraception is commonplace. Society as a whole seems to not care about others' sex lives, as long as it is not openly discussed, and as long as there are no unplanned pregnancies - out of wedlock children are highly frowned upon (they are seen as the result of a failure of responsibility).