Bots are just as fun to play against, also... Make sure when refreshing the server list that the "Show Map List" button in the bottom left corner of the menu is not ticked, it'll show up more servers that way.
If you want to change Bot difficulty, you can change it by typing "ge_bot_difficulty n", n being a number from 0 to 9.
Another option to save you opening the console everytime, once you have decided on a good difficulty for you, go to your:-
Steam/Steamapps/Sourcemods/gesource/cfg
folder and open "valve.rc" with notepad, edit the following line near the bottom of the text:-
ge_bot_difficulty n
Again, n being a number from 0 to 9. Hope this helps.