Have a large bedroom window that get's very hot late afternoon sun in the peak of summer. It has basic white aluminium venetian blinds on it that from what I am aware don't offer much in the way of heat insulation or reflective properties. The portable AC has to work very hard at this time. Is there anything I could use/hang in front of the blinds to reduce heat gain other than replacing the blinds completely?
One option that can actually help a lot and can diy done is special window film that is made just for that purpose. I have no affiliation with this company or its products but it was a first hit in a google search just to give you an idea of what I am referring to. It looks like they have some good information on their site. https://www.allwindowfilms.com/products/solar-window-film/reflective-window-film
My experience has been with a 3M product but I can't locate the product name quickly. 3M though charges a premium for their name. Is it any better or not I can't really say. These types of films do work though. Not as well as a replacement window with low-e color reflective glass multiple panes and inert gas filling. But that gets a lot more involved.
UPDATE: I found 3M's info. https://www.3m.com/3M/en_US/home-window-solutions-us/solutions/ This is the product I would probably suggest, https://www.3m.com/3M/en_US/company-us/all-3m-products/?N=5002385+8709316+8710037+8710654+8710938+8711017+8721691+3292716663&rt=rud
I'm not sure what floor your bedroom is located. Is it a first or second floor by chance? And this isn't an immediate solution. But assuming you have garden space beyond your bedroom, have you thought about planting a tree? Trees strategically and safely planted around the house can significantly reduce summer heat by providing shade for your home.
My parent's home is located on a residential side street and their living room (with a very wide and tall window) faces the street. The twenty foot tree that was cut down over a year ago truly made a difference and we didn't realize this until it was gone. Now the sun makes the front of their house so uncomfortably hot in the summer. A new sapling was put in its place but it will take a few years to gain the shade cooling effects they once enjoyed.
If it's an option, look into fast growing dwarf to midsize trees that don't have invasive roots (stay away from weeping willows - they will literally rip up your sewer drainage pipes). Ask someone at a nursery what they'd recommend.