It appears to be open to the general public and not solely for Republican party insiders or officials.
With five Republicans contesting for the party's endorsement the event should cover a spectrum of opinion "blocs" within the party as the five speak to establish product differentation.
With Bill Vikander being a first-time candidate endorsed recently by the DFL, I am urging him to attend to gain a view of that spectrum, in order to better facilitate both side's framing of issues in later debates or candidate forum events between the two candidates who end up endorsed by each party (presuming the HD 35A Republican candidates will abide by their endorsement process as the DFL is committed to abide by theirs). The Republicans are set to endorse later in the month (among delegates selected by party precinct caucusing and presumably as a closed, non-pubic event).
At a guess, Vikander would be welcome along with others leaning or committed to the DFL. However, it is likely that any intent or effort to record things for opposition use later would properly be discouraged. In the past ECM Newspapers has limited legislative district coverage to after each party is committed to its candidacies. However if the Republicans go to a primary that might gain press attention.