Yes, you can telnet into the router to set up a password. Range varies depending on structure and hardness of (concrete & steel versus wood) such - Generally good enough for the neighbors or passing cars to use it if encryption is not set up. 300 or so feet, if not more.
Linksys manual indicates a potential range in excess of 1000 feet, however, I have not checked reception at that range. At two hundred feet plus I have no problem with two or three devices connected at the same time with 3/4 or 4/4 reception. Longest indoor range (farthest bedroom to den) is about 50 feet, and no issues when in the basement. Range, of course, will vary depending upon intervening walls, wall type, trees, etc.
Setup took me all of 5 minutes. You can set up two passwords: one for the main access and one for guests, very easy to do or to change.