I'd like to know what is more important here. Is that the beard has grown quickly, or the person is just stating that s/he noticed the other person had grown a beard?
In any case "I see" would be better in the beginning of the sentence.
I brought "I see" to the beginning of the sentence.
As for your question, both meanings could be understood from this sentence, so I think both possibilities are plausible. But I think that there is some emphasis on the quickness or quality of beard growth.