If I'm understanding your issue correctly, you're on froyo and when your phone goes to sleep with wifi on and then when you wake it, the wifi is having a hard time getting reconnected? Is that correct?
If that is the case, I recommend that you do the following to change your wifi setting to Never shut down when your phone goes to sleep. Basically, what is happening is that, by default, your phone turns off the wifi when it goes to sleep and when you wake it, it takes a while to switch over from 3g back to wifi.
To change that, go into
1. Settings --> Wireless & networks --> Wi-Fi settings
2. Hit Menu --> Advanced
3. Wi-Fi sleep policy is at the top of the Advanced menu.
This also might help your battery life too since, from what I understand (but I could be wrong), wifi will use less battery than 3g and your phone won't constantly be seeking a 3g connection while it's sleeping.