Yes, indeed spectators are welcome, and there is also seating available for them. However please note all spectators are expected to be respectful of the dojo and people who are training. They must refrain from causing distraction, including talking to students while they are on the matted area or making any general noise.
All mobile phones should either be switched off or put on to silence mode, and calls should only be taken outside of the dojo / training room. Spectators are also responsible for clearing away any mess that they might leave.