Dr.Mohler wants this seminary to be as Biblical as possible. He is a Calvinist, and has not softened his stance. There is no doubt that he wants people to feel accepted here, but as long as their view can be supported Biblically. Most of the profs are Calvinistic (or lean that way, at least) but by no means do they force feed it to the students- in fact it is rarely mentioned. But you can tell it is a foundational concept that many hold.
It is without a doubt the most "reformed" but it is not a reformed seminary nor is it strictly Calvinistic. Some will play-up that aspect, it is not accurate. While most Calvinists in the SBC would want to attend here, Southern does not exclude those who disagree.
I know some hard-core Arminians (or anti-Calvinists) will try and steer people away it really doesn't matter. SBTS has seen an amazing amount of growth the past 5 years or so, and it is the fastest growing of the 6 schools. So, this effort by some has had little impact on thos who choose to attend. The PhD program here is incredible (as you should know, SBC by Grace) and is highly competitive. It is not feeling any effects of poor-mouthing.
Calvinism w/in the convention is growing and likewise those wanting a strong, conservative (calvinistic-leaning) theological training have a place to go. It juts happens to be the best SBC seminary and the most-respected academically. (is that a coincidence?? hmm)