They'll have a tough time indoors with the resulting low light and (probably) heat level.
Any reason they can't go outdoors and into the ground?

I live in a desertic area, and being mangoes tropical plants, I'm afraid they'll wither. Besides, the soil in my backyard is quite compressed and poor.

Should I be taking them outside??? Will they live in the "desertic" conditions?

Also, should I put them in direct sunlight, or is indirect sunlight fine.

Mine have been outdoors in pots since we got them. Houston has more humidity that it sounds like you have, but they made it through our drought summers. I nearly lost one wintering in our garage, but it broke out in full leaf once it got back outside. I'd try it -- make sure they get enough water. Mine have been both out in the open sun and under a patio with mostly filtered sun, but more than it appears you have in that photo.

I live in El Paso, Texas. It's supposed to be "rainy season", but taking in mind that El Paso is in the middle of a desert, we don't have much humidity nor precipitation, so the sun is harsh and the environment utterly dry. Also my backyard is full of critters and this day I experimented with the healthiest seedling I had, but after a while outside I noticed these tiny spiders running up and down the stem and the leaves, so that leaves my with two questions:

- Don't mango trees need a wet environment to thrive, or at least grow in a far more humid place?

- Managing and dealing with the critters (mainly bad or pests) wouldn't mean an extra effort and extra money wasted?