Should I repot it right now or should I wait for the new growth start?

I would wait until the first sign of root growth You will damage some roots during repotting and you don't know how long until new ones will grow. Even if the medium isn't great right now, you don't need to water this species much, if any, this time of year, so there is little risk of root rot.

One question...since I got the Lealia, 8 days ago, never watered it. I was thinking about misting the top medium to increase humidity near the roots but weather is still unstable temperature wise. Next 6 days max temps are forecast to be 16 ºC avg (60 F), no sun, and then increase to low 70's (with sun).

The room where I've put it has night temps in the low 60's by night and high 70's by day (with sun). Without sun max temp is mid 60's.
HR is in low 40's/high 30's.

Maybe it's still too cool to give it the extra humidity by misting the top medium.

What do you think I should do at this point?

I would not mist. It often has very low relative humidity at the end of winter in habitat.

My immediate doubt was cleared. Thanks

Now, another one... under what conditions should I start watering? I know it should be when the roots start to grow but do they start growing without a humidity increase?

This is just a guess... the roots start growing at the end of winter. Summer rains usually come the first week of May. Perhaps the plant is trying to be ready for water availability, for it only rains 4 -5 months of the year.

I'll keep monitoring it very closely.
If I see no activity, when I notice a max temp stabilization over 22 ºC (71,6 F) I'll start a light watering to act as a catalyst for root growth.
In their habitat heavy rains start in June but here we reach those temps by April/May.
So, starting on the 22 ºC, from there it's always uphill.:biggrin:

In their habitat, in the cool season, HR is around 60-65%. Since I have under the low 40's, in the meawhile I'll mist lightly the top of the medium once/week or more, depending on the weather.

Note: I'm putting it under full sun for an hour followed by 1/2 hr of bright shade. So far no burns or damage.

I am very late to this party... but Guarianthe (formerly Cattleya) aurantiaca may be an option.

Cattleya aurantiaca - Cattleya Source

From what I understand of it, it is one of the most northern growing Catts. I have a division of a large variant of this guy. Mine's been very easy. Last October, it had no roots. I mounted it and now it's in bud and has a bazillion (exaggeration) roots. Mine has not experienced the 40's, but probably close. I keep it in the "cool" room with the Masdevallias and it is in the window that has probably experienced regular drops into the low 50's when it gets really cold outside.

Thank you for the sugestion, Salixx.
Unfortunately this specie also has the same problem as mexican laelias: dry winter.
My goal was to let them outside all year but I can't provide them a dry winter and I don't have conditions to protect them.

Now the temps are consistently aqual or higher than 20 ºC (68 F), with forecasts of low 80's, with clear skies, today I gave it a little water with a spray bottle in the hopes it will ignite some growth. This was the first time it "saw" water since I bought it, two weeks ago.

I've found also this...it was there already but I haven't noticed it. I don't know if it has been growing or not. One thing I know: it has no new roots.

http://i1343.photobucket.com/albums/...ps2rjktj3w.jpg
http://i1343.photobucket.com/albums/...ps2q6dzfba.jpg
http://i1343.photobucket.com/albums/...psglaf1bo8.jpg
http://i1343.photobucket.com/albums/...ps1rn2fdo0.jpg