Hey PG, don't dry out citrus seed. Just clean off the fruit and plant, keep moist. Next time you go over to your Mom's, get some fresh seed.
This is pretty much it....not hard to do at all

http://www.ehow.com/how_6178163_plant-meyer-lemons-seeds.html

They will take a long time to fruit from seed, I would just buy one myself....

Mangos are hybrids, there's no telling what you'll get from a seed and again a long time to fruit. Shop around for a good variety for you area - might give Pine Island a call. They will ship to you too.
If you want your Mom's mango, I would find someone to graft it. That way you'll get the exact same one...

Good luck, HTH
Corrie

PG, here's how to root cuttings from your Mom's lemon too. That would give you a bigger tree faster, and fruit faster too.....

http://www.ehow.com/how_5873735_propagate-lemon-tree-cutting.html

Here is a link that might be useful: How to root Meyer cuttings

Iam in Tampa and I have a Meyer and Improved Meyer in my yard and they are amazing producers and the blossoms IMHO are the best smelling of all the citrus blossoms. Right now my entire yard is perfumed in Meyer blossom deliciousness.

Meyers do very well in Tampa, they may do LESS well in Lakeland b/c it gets colder there. I would not advise you to start from seed or cutting. It will take YEARS before you get anything. Go to one of the many area garden centers that have good citrus tree selection and buy the biggest Meyer tree you can afford.

Save yourself a lot of trouble and get one at one of the big box stores. I planted one a year ago in "soil" I had to use a pick axe to get through. The tree is thriving, covered with still green lemons, and lots more flowers. I do feed it and water when necessary, but it's doing better than any of the other things I've planted. Now I've got to figure out what to do with all the lemons.

Citrus is very easy to airlayer that way you could get an exact clone of the mother plant but hers is probably grafted so you might either want to graft one onto an existing roostock or just buy one. I have a couple grafted Meyers lemons that I got from Home Depot. They are loaded down with fruit. I am keeping them in large pots for now since I am near the Jax area.

You could also weigh down a branch and set a brick on it and cover a few nodes with soil to get an air layer. I had a buddah's hand branch that kinda fell down and rooted itself in 4 different places and made a huge buddah's hand fruit underneath the soil!! LOL. In the winter, when I moved the pot, I cut that branch into 4 pieces and now have 4 new little trees.

can anybody share some seeds of Meyer lemon with me? I've been looking online and they are veeeery expensive and I'm in a tight budget.

In the spring, Lowes usually has small lemon and lime trees, as well as others for $10. They grow quickly and fruit in a year or two at the most.