There is a hadith that has roughly this content: a man was being chased by people who wanted to harm him, and I think kill him. They entered his wife's house and asked where her husband is. She drew a circle on the ground without them noticing and pointed to it while she said "he is not here" so she doesn't lie about him being "here". That illustrates the severity of taking not lying seriously in Islam.
There are even ahadith that seem to imply that lying in order to make a joke is haram, but I think that there is some unclarity about the case where everyone who hears it is fully aware that it is a lie for joke effect.
Other ahadith refer to the seriousness of repeating a sin in Islam, mentioning something like "a person lies and keeps lying until they become a liar through and through", meaning repeating a minor sin makes you accustomed to it and carries heavier moral judgement than committing a major sin (say, fornication, homosexual acts, drinking, shouting at your parents) once and abandoning it.
So yes, what you describe carries the judgement of being haram in Islam. From the perspective of Islam, you are expected not to lie for convenience.
An effective way of dealing with those things is saying polite things like "sorry, not today" or "that's outside my comfort zone"; you might want to explain your position to the guys. If you lie to female friends for religious reasons as well, long-term, your best policy would be honesty and disclosure; that way the friendships, if you value them, have a chance of surviving. Seeing how you bother to make pretenses, I assume you do value the friendships.
Disclaimer: I am not a muslim.
