Just do this, look for the Lati@s, escape from it, DO NOT SAVE IT, then check on your map where it is (usually in rt 126 or 127) then when you find it, catch it, if your not happy with the nature or stats, reset it and do all this again. If you dont care what nature it is, then save it just after you see it for the first time (theres no diifference when you catch it after you save it the first time, even if you catch it the first time, the nature will not change, you have to save it before seeing lati@s the first time if you want a different nature.)
Its just advice but its definately true, I tried getting a good nature like Calm but my Latias' nature is Serious in Emerald and I dont really like that nature 2 much... (just cause the way the word looks, :D )
Its not just for Emerald, its also Ruby and Sapphire too, dont get tricked by it...