Two and a half weeks is nothing for China! It's a very big country with a lot of variety. Don't worry about the language - get a phrase book (with characters, not just pinyin) and a guidebook that has characters for place names, and always carry your hotel's card.

As thursdaysd says, there is a great deal to see in China - it is huge! And she gives very good advice about managing the language. Learn a few very basic phrases (thank you, hello) and bring a book that has Chinese characters for basic phrases and place names.

I would not recommend expanding your trip to other countries - there is more than enough to see in China! And if you go elsewhere, you'll just have to deal with extra transit time and other languages. My recommendation is to take advantage of this opportunity to see a bit of China with the freedom afforded by solo travel.

Enjoy!

You'll be fine with a few easy phrases! Hello and thank you are very easy to learn and if you have those, you're set. For everything else, a simple phrase book or travel guide is usually easy enough. When I needed to ask something odd, the staff at the hotel desk were happy to write down the characters for me.

When I left home I had a couple pages (one for each city) with the locations I wanted to go printed in English and in Chinese characters. That way I could just point to the place I wanted to go and look hopefully at the taxi driver. Menus usually either had pictures or had English translations. Again, pointing with a smile works wonders.

Most of the people I dealt with as a tourist either spoke English, spoke enough basic English to try to sell me something (we bargained using a calculator to show prices) or were happy to laugh and use charades with a silly American. Smile, have fun and you'll be fine!

2.5 weeks is perfect for China. I spent about a week in Beijing, about 3 days in Xi'an and about 2 days in Shanghai. I could have happily spent a couple more days in Beijing. Remember to give yourself a little extra time in your first city incase of jet lag.

2.5 weeks is barely enough to scratch the surface of China. Don't even think of other countries. Remember that distances are such that you would waste a lot of time traveling.
Language is not an issue. In such a short time you will likely visit places that are well travelled by many tourists before you.

International flights from China to elsewhere is not cheap, but not everybody has to like traveling in China. I don't know why you're in Shanghai in the first place, but traveling in China is not always enjoyable. I live in Hong Kong and have traveled in China fairly extensively, but if I have a 2.5wk vacation from Shanghai and cost is not a big factor, I'll go to Japan or Korea or even Taiwan.

rkkwan - those are certainly worthwhile destinations (my pick would be Taiwan, which sometimes felt more Chinese than China), but for a first time visitor, who has already gone to the trouble and expense of getting a visa, it seems perverse not to see more than Shanghai (hardly my favorite Chinese destination).