If I do not have anyone to practice speaking with, will reading Mandarin help me speak Mandarin?
It should help! Reading generally helps to improve your grasp of grammar and vocabulary. If the sentences are from real life speaking situations, then that also will help.
reading can be one of a number of complementary ways of studying the language. The website hacking Chinese has lots of useful resources on optimising your study techniques. Here's a link to a group of resources related to reading: link; and here's the link for the resources on speaking: link.