Is there any risk of illness from eating fresh avocados and/or guacamole?

Yes. Avocados can harbor salmonella or E. coli O157:H7, depending on how they were harvested or processed. These pathogenic bacteria can be transferred from avocado to avocado by human hands or contaminated processing equipment.  The bacteria reside on the avocado's tough outer skin but can be transferred to its pulpy interior when the avocado is opened.
 
Depending on the condition of its raw ingredients, as well as the conditions under which it was processed, store-bought guacamole also may harbor pathogenic bacteria. The good news is that the guacamole is pasteurized during processing, minimizing the likelihood that the finished product harbors  E. coli or salmonella. The pathogen Listeria monocytogenes may be another matter, particularly if pasteurization occurs before the guacamole is packaged. Listeria thrives in dark, dank environments such as those used to process guacamole. Because air, dripping water, storage freezers, and processing equipment can harbor listeria, guacamole can become tainted after pasteurization but prior to packaging if proper sanitation protocols aren't followed. 
 
Due to food-safety concerns, fresh avocados, tomatoes, onions, and similar ingredients require special handling when preparing homemade guacamole. Improper handling can lead to cross- contamination of the ingredients and final product.   
 
Both avocados and guacamole are subject to spoilage bacteria or mold growth as a result of improper storage or proper storage for a prolonged period of time. All perishables have their limits. Spoiled or moldy guacamole or guacamole ingredients should be discarded.
 
Fortunately, proper storage, handling, and preparation of guacamole eliminate most risk of illness.
 
Source(s):
FDA-USDA "Safe  Handling of Raw Produce and Fresh-Squeezed Fruit and Vegetable Juices" 
Avure.com "Ultra High-Pressure Guacamole"