adopted stray pup

Question
Two days ago i adopted a puppy i found on the street. The vet said she's not of any breed. Estimated 2 months old. She weighed 3.7 pounds and has almost all her teeth. The molars are still small, but she does eat dry dog food. Could you tell by the description if she does sound about 2 months? And with the weight and age, can you estimate how big she'll be when fully grown?
I kept her in my room in an open box, she woke me up like every two hours at night, i took her out, and she did her business outside. I haven't crated her, but i just got a "pet-taxi" thing. I don't know if i should put her in there when i'm away. I don't want to ruin her instinct to go potty outside by leaving her in there too long. She doesn't like it though, i left just the bottom part near my bed at night and put her to sleep there, but later she got up, she fell asleep on the floor. It seems she likes the floor better. She hasn't destroyed or chewed on anything, but she has tried to nibble on my shoes and sheets. When I have been away, i have left her outside. It seems she cries for a while, but she does entertain herself with the grass and plants. So, should i continue to leave her like this?
Also, what should i be teaching her and how? She seems to learn quickly, i don't want to mistakenly teach her the wrong things.

Thank you very much for the advice you can give me!

Answer
8 weeks sounds about right.

She wont be very big if this is her weight just now.

I wouldnt ever ever leave a dog outside.

Teach her basic obedience which you will find here.

http://home.att.net/~vlea/Basic_Dog_Obedience.htm

http://www.perfectpaws.com/whytr.html

http://www.cityofdunedin.com/city/?page=animal_obey