My teacher, who is a native Japanese, definately stressed it to mean 'at least'. Here's another example from my text:
毎日4時間も勉強したのだから、明日のテストでは(最低)70点ぐらいは取れるだろう。
He said that even without 最低 it still expresses "at least". Here are some example sentences from alc.co.jp
# 飛行機の切符ぐらいは僕に買わせてくれ。
At least let me buy you an airline ticket.
# 壁にボールを投げてくっ付かなくても、跡ぐらいは残る。
If the ball does not stick to the wall, it will at least leave a mark.
This one uses 少なくても:
あらまー!少なくとも1時間はかかったでしょう!
Oh, no! I bet it took you at least an hour!
This one doesn't:
どのくらい時間かかると思ってるんだよ。8時間はかかるぞ。
How many hours do you think it will take? It will be 8 hours at least.
Here's another one that has been translated as "at least" without using 少なくても or 最低:
# 「何日くらいで退院できますか?」「1週間はむりですあ ヒ」
"How soon can I be released from the hospital?" "You have to spend at least seven days here."
Most of them, however, do use either 少なくても or 最低. I'd just like to know what the nuance is with and without.