Can I change menu font size?

I am running OS X Ver 10.6.4. My problem is that some fonts are way too small to comfortably read. For example, when using iWorks Numbers, the column & row numbers are very small. In Mail, if I start a new email, I cannot read anything less than 12 points. Since I am a recent convert from PCs, I was accustomed to be able to change these fonts through the display preferences. I've tried changing the resolution, but nothing really seems to help. Is there anywhere I can go to change this?

BTW, this is what is says under About this Mac - Displays:
ATI Radeon HD 4670:
Chipset Model: ATI Radeon HD 4670
Type: GPU
Bus: PCIe
PCIe Lane Width: x16
VRAM (Total): 256 MB
Vendor: ATI (0x1002)
Device ID: 0x9488
Revision ID: 0x0000
ROM Revision: 113-B8030C-253
EFI Driver Version: 01.00.367
Displays:
iMac:
Resolution: 1920 x 1080
Pixel Depth: 32-Bit Color (ARGB8888)
Main Display: Yes
Mirror: Off
Online: Yes
Built-In: Yes
Display Connector:
Status: No Display Connected

You can't change the menubar or menu's fontsizes but virtually every application will have settings in their preferences for fonts. ie: Mail (menu) > Preferences > Fonts & Colors will allow you to customize the mail interface font sizes.
And in the finder go to View (menu) > view options and you can change the font size for folders and such.

I think it's more a question of the visibility of the font, rather than just the font size. I think I should be able to read a size 12 font without straining. I can change the font size, but if I'm sending an email, I don't want to have to type it 24 font in order to see it, and then send it with this large font.