If it's the e desktop, switching to presentation mode could get you what you want (In fact, if I remember correctly, it would issue a message like You are now entering Presentation mode; certain options such as screensaver and screen blanking will be disabled. Give it a shot
Avoid tacking a different issue to your original problem. Someone else could be searching for the answer to autologin as guest, but changing the topic or adding a different issue adds "noise" to his search results. For next time, it would be better to open a new thread to discuss or troubleshoot a separate item. This rule of netiquette applies to any forum, not just Bodhi's.