No, they aren't clearly bi-sexual. They are heterosexuals engaging in pagan ritual sex with prostitutes. There is no indication of an enduring pattern of emotional and physical attraction. A sex act does not determine a sexual orientation.<quoted text>
Heterosexuals who commit homosexual acts are clearly bi-sexuals, but Paul is explicitly referring to both Lesbians and Gays:
"Because of this (worshipping things instead of God), God gave them over to shameful lusts. Even their women exchanged natural relations for unnatural ones. In the same way the men also abandoned natural relations with women and were inflamed with lust for one another. Men committed indecent acts with other men, and received in themselves the due penalty for their perversion."
Additionally, it is clear this passage isn't describing committed adult relationships built on love and mutual respect. They were having orgies in the temple, not forming families.