Imrpoving WiFi signal for an android device

You said your laptop gets good signal when the other devices don't. You can share that connection with other devices using the built in ICS (Internet Connection Sharing) that is already a part of Windows. ICS can be configured manually but it is much easier using a program called Connectify, which is available for free.

If you had a cheap USB wifi adapter, Connectify would take your laptops main wifi connection and share it with your other devices. The trick is having 2 network adapters on the main PC. I used Connectify to share my wired connection on my desktop with my wireless ps3 and our iPhones. I used a cheap wifi PCI card to set this up.