You dont need a library card to come and hang out. There are certain areas you can come and read peacefully. Unfortunately there are some patrons that can be a little colorful so I would advise trying the 4th or 5th floors. Also there are many branches that have beautiful quiet spaces to read.
You do not need a card to use the library, only to take books home or use their computers. However, be warned: The library smells like homeless people- a combination of body odor, feces, and stale beer. However, the farther up you go, the better it is, so go 3rd floor or higher. The fifth floor magazine area has a beautiful glass ceiling and is very quiet.
You don't need to have a library card to enter or access wifi. In addition to what has already been said, there's a lovely children's area where they monitor to make sure adults not accompanying children aren't causing problems, and an area for teens where younger children and adults are kept out. This library has a great selection and is fun to browse, and there's always something tempting in the Friends of the Library book sale area. Due to its location, the restrooms and entry area can be rather less than clean but everything else is great.
Thanks! Your answer is awaiting moderation.