There are still people out there who arent attracted to trans people, and it shouldnt be their fault if theyre not interested. Everybody has the right to refuse a relationship or intimacy regardless of the reason, even something as dumb as they didnt like your hair.
If you try to hide the fact that you werent born X and they notice based on physical traits, then that'll make them really uncomfortable and betrayed. If you are a man or a woman that's fine but the fact of the matter is you were not born that way, no matter what you do nothing is going to replace your history or some few aspects of your physical nature. You are still transgender, you will always be transgender, its part of who you are/were.
People are never obligated to have sex with you if they have preferences no matter how misguided, short sighted, or picky they are.
Not only that, but besides the emotional fragility of straight human nature for not wanting to have sex with someone trans (Some straight people arent necessarily bigots but prefer not to for some reason, others legitimately have some outlandish fear that they might be attracted to a woman or man who wasnt born that way), the idea of trying to have sex stealth is potentially dangerous and risky depending on the type of person you take to bed. If you take a bigoted person, they could cause physical harm if upset or angry, or they might socially embarass or ostracize you.Not only that but as stated above, fragile straight cis people have a fragil sex ego, if they have sex with the wrong person it can cause a stir or panic for other bigoted people and form more hate against trans people. Its a risk that isnt safe for you and isnt fair for your partner.
If you absolutely must try to be stealth, its best to know for a fact that the person is pansexual/bisexual or lgbt friendly beforehand before attempting sexual intercourse. Anything else is dishonest, you're inadvertantly/indirectly violating sexual consent and that's not okay